Urticaria

Urticaria, commonly called hives, is a skin disorder in which itchy, raised wheals and sometimes deeper swelling called angioedema appear suddenly and usually fade within hours. It is driven mainly by mast cells in the skin, which release histamine and other mediators that make small blood vessels leak fluid. Because the disease is so varied in its triggers and course, it is a frequent reason for consultation in allergy, dermatology, and general medicine practice.

Most episodes are benign and self-limiting, but the condition matters for several reasons. Chronic forms can last for years, disturb sleep, work, and school, and are often accompanied by psychological distress. Swelling of the tongue or throat can obstruct the airway and is a medical emergency. In some patients, urticaria is also linked to autoimmune disease, infection, drugs, or rare systemic disorders, so its evaluation can reveal other conditions.

This entry first defines urticaria and its clinical features, then sets out the classification by duration and trigger, including the inducible physical and non-physical forms. It goes on to describe the immune and cellular mechanisms, the autoimmune subtypes of chronic spontaneous urticaria, and the known causes and associated diseases. The final sections cover epidemiology, diagnosis and differential diagnosis, treatment, prognosis, and the history of research together with unresolved questions.

Definition and clinical features

Urticaria, commonly called hives, is a rash made of wheals: raised, itchy lesions that look pale or red. Wheals are erythematous, pruritic swellings caused by fluid in the skin Hmm, I'll rewrite that line below.

Urticaria, commonly called hives, is a rash made of wheals, which are raised, itchy patches of local skin swelling that appear pale or red. The lesions are erythematous and pruritic, reflecting cutaneous oedema. Pressing on the centre of a wheal blanches it, but a ring of redness around it, called the flare, remains. The lesions blanch under pressure while staying encircled by a flare of erythema. The rash can consist of wheals, deep swelling, or both, and it is an inflammatory disorder without systemic symptoms.

The defining feature of an individual wheal is that it is short-lived. Wheals resolve in under 24 hours by definition. Clinicians therefore treat a lesion that lasts longer as an atypical finding. If individual lesions persist beyond 24 hours, urticarial vasculitis should be considered. The wheal-and-flare pattern itself is produced when vasoactive mediators released from mast cells and basophils act on local blood vessels, a mechanism discussed in the pathogenesis section.

Angioedema is the deeper counterpart. Where wheals sit in the upper dermis, angioedema involves rapid swelling of the deep dermis, submucosal tissue and subcutaneous tissue. It is usually non-itchy and more often painful or burning. Typical features include localised swelling that is skin-coloured or slightly red, is not itchy, does not pit, and usually settles within 24–48 hours. Common sites include the eyelids, lips, genitals, hands and feet. Involvement of the tongue, throat and airway is more dangerous, and intestinal angioedema is painful and can mimic an acute abdomen.

Reported durations of angioedema differ between sources. One guideline states that resolution occurs within 72 hours, a clinical handbook says it generally lasts less than 48 hours, and DermNet gives 24–48 hours. The longer course, compared with wheals, is commonly attributed to the deeper tissue layers involved, though the detailed mechanisms are discussed later in this entry. Angioedema can also occur without wheals. In bradykinin-mediated cases, the superficial layers of the dermis and epidermis are usually spared, so urticaria and pruritus are absent.

Symptom burden centres on itch. Chronic urticaria is commonly described as presenting with intensely itchy wheals. Individual wheals usually fade without bruising or scarring. Wheals resolve spontaneously within 24 hours and leave no residue on the skin. Angioedema, by contrast, is the component that can threaten life. It becomes life-threatening when the larynx is involved. When swelling of the tongue or upper airway develops quickly, breathing may become difficult, and emergency assessment is required. Recognising airway involvement is therefore the most important early step in managing a patient presenting with urticaria or angioedema.

Classification by duration and trigger

Urticaria is first sorted by how long it lasts. Acute urticaria is wheals, angioedema, or both lasting six weeks or less, and chronic urticaria is the same pattern lasting longer, as defined by the 2022 international guideline. The chronic category does not require constant symptoms: chronic urticaria can present with daily or almost daily signs and symptoms, or with an intermittent or recurrent course.

The six-week line is a convention rather than a biological boundary. The guideline's rationale is that acute, self-limited episodes tend to subside within 1 to 3 weeks, so a cutoff at 6 weeks makes an exogenous cause of the process unlikely. The two categories also differ in their causes and prognosis, and in how they are approached. Recent reviews describe the threshold as practical for clinical classification but insufficient to capture pathogenic diversity. Some acute cases progress to chronic disease, particularly those with autoreactive markers, low basophil counts, or thyroid autoimmunity. For that reason, a chronic diagnosis also requires that the protracted pattern is not simply a run of repeated acute episodes.

Spontaneous versus inducible urticaria

The second axis asks whether a definite trigger can be identified. Chronic spontaneous urticaria is characterized by symptoms not elicited by apparent factors, whereas inducible forms require a specific stimulus such as sunlight, pressure, friction, or heat or cold. The word "spontaneous" separates this group both from urticaria with an identifiable cause, such as medication reactions, and from physical forms. Triggers can still aggravate spontaneous disease: about 30 percent of patients with CSU have some episodes induced by physical factors. The categories are therefore useful but not perfectly separated.

Why "idiopathic" was replaced

The older term "chronic idiopathic urticaria" grouped every chronic form without a known trigger. As testing improved, autoantibodies were found in some of these forms. Because the hives still appear unpredictably and are not induced by a demonstrable trigger, the 2013 guideline revision adopted "chronic spontaneous urticaria" (CSU) to reflect this heterogeneity. The use of "chronic idiopathic urticaria" in medical practice is no longer recommended. Because the newer category is broader, some cases once called idiopathic, such as those with a known autoantibody or an infection-related onset, are now placed under CSU rather than treated as unexplained.

Subdivision and proportions

Chronic urticaria is divided into chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU), the latter including physical and non-physical forms. Published estimates of CSU's share vary. One source reports that two out of three cases of chronic urticaria are spontaneous, while UK guidance gives a range of 60–80%. The same UK guidance also states a figure of 95% in its introduction, which conflicts with its own range. The spread reflects differences between populations, referral settings, and how mixed presentations are counted.

Terminology and research consistency

Terminology has changed repeatedly. CIndU replaced the older label "physical urticaria" and now also covers cholinergic and aquagenic forms. The 2022 guideline recommended keeping the current classification of chronic urticaria, with at least 90% agreement among the experts consulted. Consistent labels matter because trials, registries, and comparisons between studies depend on the same patients being grouped the same way. Older papers that use "chronic idiopathic urticaria" or "physical urticaria" may therefore not be directly comparable with recent CSU or CIndU data.

Types of chronic inducible urticaria

The current international classification divides chronic inducible urticaria (CIndU) into two branches: physical urticarias (dermographism, delayed-pressure urticaria, exercise-induced urticaria, cold urticaria, heat urticaria, solar urticaria, and vibratory urticaria) and non-physical urticarias caused by exposure to specific stimuli (cholinergic urticaria, contact urticaria, and aquagenic urticaria).

Mechanical and pressure-related forms

Symptomatic dermographism is the commonest physical form. Wheals develop within a few minutes of stroking the skin. Delayed-pressure urticaria is different: swelling that hurts is its hallmark, and it emerges after 3–12 h of sustained pressure. Vibratory urticaria completes the mechanical group, with vibration as its only stimulus Vibration.

Temperature, light and water

Cold urticaria is set off by cold air, water, or a cold object. Reactions can be localised or diffuse, and can be accompanied by angioedema within minutes after exposure. It accounts for approximately one third of physical urticarias, and cryoglobulins are only occasionally responsible Cold-induced urticaria is rarely caused by cryoglobulins..

Heat urticaria is very rare. Holding hot objects, eating hot food, or entering hot surroundings can bring on wheals within minutes in susceptible patients. Solar urticaria is triggered by UV or visible light, and because its lesions can look like sunburn, it is sometimes mistaken for other photosensitivity disorders Solar urticaria can be mistaken for sunburn or another form of photosensitivity.

Aquagenic urticaria is provoked by water at any temperature, and its wheals tend to cluster on the upper body generally affect the upper part of the body. Exercise-induced urticaria, which some classifications count among physical forms, is closely linked to the cholinergic group discussed below.

Non-physical forms

Cholinergic urticaria is the best-known non-physical type. The usual trigger is a rise in core body temperature, produced by exercise, fever, or external passive heat such as a hot bath or shower, although emotional stress and spicy food can also provoke it. The lesions are small, intensely pruritic wheals surrounded by large erythematous flares. The condition mainly affects adolescents, young adults, and atopic patients. Its mechanism remains incompletely explained: the rash is triggered by activation of cholinergic sympathetic innervation of sweat glands, but the mechanism of this remains unclear. In some patients the same stimuli escalate to multisystem reactions that can be life-threatening, so anaphylaxis must be considered.

Contact urticaria develops when skin or mucosa meets a substance, through either an immunological or a non-immunological route (Non)immunological contactant. A mucosal variant, oral allergy syndrome, occurs when people sensitised to pollens react to certain plant foods because of cross-reacting IgE.

Frequency and identification

Estimates of how common each form is remain uncertain. Symptomatic dermographism and cholinergic urticaria appear to be the most common forms, but no reliable data exist. Reported shares of physical urticaria among chronic urticaria patients vary widely: one systematic review gives 7% to 44%, while other series place it at 10% to 50% of patients with CU.

Overlap is common. CIndU occurs concomitantly in 7% to 30% of patients with CSU, and up to 36% of patients with CSU have been reported to react concomitantly to physical trigger tests. A single patient may also carry two or more forms of CIndU, so each form should be sought separately.

Identifying the trigger is the first clinical task. Diagnosis rests on a detailed medical history, physical examination, and provocation (challenge) tests. Challenge tests use stroking, direct pressure, cold exposure, exercise or hot water, sunlight, room-temperature water, and vibration to reproduce the reaction Procedures to trigger urticaria (the challenge testing) include dermatographism (stroking the skin), delayed pressure urticaria (direct pressure), cold-induced urticaria (cold exposure). Because provocation testing is central, laboratory investigation has a very limited role in the diagnosis.

Pathogenesis: mast cells, basophils, and mediators

Effector cells and their mediators

Skin mast cells are generally regarded as the principal effector cells in chronic urticaria. Histopathological studies show skin mast cell degranulation alongside a perivascular infiltrate of lymphocytes, eosinophils, neutrophils, and basophils. Basophils, the circulating counterparts of tissue mast cells, share several features with them: both are granulated, both contain histamine and heparin, and both release histamine when IgE binds their high-affinity receptor. In CSU, blood basophil counts have been reported to fall as disease activity rises, which has been read as evidence that these cells move from the bloodstream into lesions.

Mast cell products fall into two groups. Preformed mediators stored in granules, including histamine, tryptase, and other proteases, are released within minutes of activation. Newly synthesized mediators, such as leukotrienes, prostaglandin D2, and platelet-activating factor, follow, along with cytokines including IL-4, IL-13, and IL-31. Histamine is the best-established driver of wheals, but its effect is brief, since its half-life in tissue is only about 10 to 30 minutes. A 2005 review found little convincing evidence that the newly generated products play a significant direct role, whereas later work emphasizes that de novo cytokines and chemokines recruit leukocytes to the lesion.

From mediator release to wheal and angioedema

Histamine acting on H1 receptors causes vasodilation and raises vascular permeability, so plasma leaks into the superficial dermis. This fluid accumulation forms the wheal. The surrounding flare reflects dilated small arterioles, classically explained in part by an axon reflex. Itch arises because histamine, tryptase acting on PAR1 and PAR2, and cytokines such as IL-31 stimulate sensory nerve endings in the skin.

Angioedema involves the same basic process extending into the deeper dermis and subcutaneous tissue. In this layer, newly produced chemokines and cytokines draw eosinophils, basophils, T cells, and neutrophils out of the circulation, and this cellular infiltrate is thought to contribute to the longer-lasting swelling. Histamine also acts on endothelial cells to induce tissue factor, which leads to C5a generation that in turn acts back on basophils and mast cells, forming a feedback loop between the vessel wall and effector cells.

Routes of mast cell activation

The best-known route is the classical type I hypersensitivity pathway. Specific antigen or an autoantibody bridges two neighbouring alpha chains of the high-affinity IgE receptor (FcεRI), which triggers degranulation. Signalling through Bruton's tyrosine kinase (BTK) is required for this response in both mast cells and basophils, which is why BTK inhibitors are being studied. A second route runs through the complement cascade: activation produces the anaphylatoxins C3a and C5a, which can release histamine directly, and C5a levels have been reported to be raised in some patients with CSU. A third route is non-immune. Some drugs and physical stimuli degranulate mast cells directly, without IgE, largely through receptors rather than antibodies.

Newer receptors and anti-IgE non-response

Mast cells express receptors that can be activated independently of FcεRI. These include MRGPRX2, which responds to a range of drugs and to neuropeptides such as substance P, as well as C5aR, PAR-1, PAR-2, CRTh2, and cytokine receptors. Activation of the coagulation cascade and of eosinophils has also been described as an alternative route. Elevated MRGPRX2 expression has been reported on basophils from patients with chronic urticaria, both at rest and after stimulation, although in one small study substance P itself did not activate those basophils.

These alternative pathways help explain why omalizumab, an anti-IgE antibody that binds free IgE and reduces FcεRI expression on mast cells and basophils, does not work for every patient. Response to anti-IgE treatment can be rapid, delayed, or absent. A working hypothesis is that in non-responders, degranulation proceeds through FcεRI-independent routes that omalizumab does not block. Consistent with this, one study found that anti-IgE-induced basophil degranulation rose more over time in clinical non-responders. In vitro, the BTK inhibitor remibrutinib suppressed mast cell and basophil activation triggered by patient sera regardless of omalizumab response, although these laboratory findings have not been established as a clinical predictor.

Autoimmunity and the subtypes of chronic spontaneous urticaria

Type I (autoallergic) CSU

Type I CSU is defined by IgE antibodies that recognise the patient's own molecules rather than external allergens. Type I autoallergic CSU is mediated by IgE autoantibodies against self-antigens such as TPO and IL-24. Other reported targets include dsDNA, tissue factor TF, IL-24 and TPO. These IgE antibodies bind to the high-affinity receptor FcεRI on mast cells and basophils and trigger their degranulation. Compared with type IIb, this group generally shows higher total IgE, and it is considered the more common of the two endotypes. Autoallergic CSU (aaCSU; also sometimes called type I CSU) is linked to IgE autoantibodies and more common than autoimmune CSU (aiCSU, also called type IIb CSU).

Clinically, type I patients tend to respond rapidly to omalizumab, the anti-IgE antibody. In one randomised trial of antihistamine-resistant patients with IgE autoantibodies to TPO, 70% of patients showed complete protection from wheal development versus 4.5% in the placebo group. Early responders typically improve within the first weeks of treatment, and the rapid fall in free IgE is thought to deplete the pathogenic IgE autoantibodies.

Type IIb (autoimmune) CSU

In type IIb CSU, the effector antibodies belong to the IgG class. Type IIb autoimmune CSU is driven by IgG antibodies against either IgE or the high-affinity IgE receptor (FcεRI). Because these antibodies are generated against the immune system's own components, type IIb is regarded as a true autoimmune mechanism, in contrast to the classical allergic type I hypersensitivity that involves exogenous allergens.

Type IIb patients have a characteristic clinical and laboratory profile. Type IIb autoimmune CSU is characterized by higher disease severity, concomitant autoimmune diseases, low levels of total IgE, elevated levels of IgG-anti–thyroid peroxidase, basopenia, eosinopenia, poor response to antihistamines and to omalizumab, and a good response to cyclosporine. Female predominance is strong; one summary table lists 87%-93% of type IIb patients as female. Diagnosis is typically based on a combination of tests: a positive autologous serum skin test (ASST), the presence of functional IgG autoantibodies (e.g., IgG-anti-FcεRI/IgG-anti-IgE), and a positive basophil activation test (BAT) or basophil histamine release assay (BHRA).

Overlap and the limits of classification

The two endotypes are not always cleanly separable. In one study, more than 50% of patients had coexisting IgE and IgG autoantibodies to 1 or more of the 4 autoantigens assessed. Other work has suggested that most patients with type IIb features also show type I features, though this finding needs confirmation in larger cohorts. Consequently, strict dichotomous classification is insufficient, as many patients display concurrent IgE- and IgG-mediated autoreactivity, and some authors describe an immunological continuum instead. Published estimates of the proportion of patients with no detectable autoantibodies vary with the assay used and the diagnostic criteria applied, and no single figure is generally accepted.

Response to omalizumab and second-line therapy

The distinction matters most for treatment. Because omalizumab targets the IgE–FcεRI axis, it is generally more effective in patients with the type I autoallergic endotype of CSU, whereas patients with type IIb autoimmune CSU tend to exhibit a slower and often less robust response to anti-IgE therapy. Low baseline total IgE is also associated with poor response. In one prospective observational study of 83 patients, non-responders had markedly lower baseline IgE than partial responders. Nonresponders are thought to include a subset of type IIb patients, who may respond better to ciclosporin (cyclosporine), a second-line immunosuppressant used off-label in many settings. Thyroid autoimmunity alone has not proved to be a reliable predictor of omalizumab response, whereas IgE levels have shown a strong association with it.

Non-autoimmune contributors

Not all mast cell activation in CSU can be explained by autoantibodies, and several other pathways have been studied. The coagulation system is among the most investigated. Tissue factor expressed on endothelial cells and eosinophils activates the extrinsic coagulation pathway, followed by leakage of plasma from blood vessels and mast cell activation. Thrombin formed in this process can further generate C5a, which selectively activates skin mast cells. Histamine itself appears to reinforce this loop, since the expression of TF on endothelial cells is synergistically enhanced by the activation of Toll-like receptors and histamine H1 receptors.

The complement system contributes through C5a, an anaphylatoxin. Histamine-induced expression of tissue factor on endothelial cells initiates the extrinsic coagulation pathway, leading to the production of complement 5a (C5a), which subsequently activates both basophils and mast cells via the C5a receptor (C5aR). Endothelial cells are also directly implicated in the wheal, because resulting EC activation promotes vascular permeability.

Eosinophils are a third focus of interest. Emerging data suggest that eosinophils may play a more integral role in the pathophysiology of CSU than previously assumed. Much of this framework remains hypothetical and rests on in vitro work and small clinical studies. Current reviews generally view these pathways as amplifiers of disease activity and treatment refractoriness rather than as a complete explanation of initiation, and their relationship to the autoantibody endotypes is still unresolved.

Causes, triggers, and associated diseases

Urticaria often has no single identifiable cause, and the balance of possible causes differs between acute and chronic forms. Acute episodes frequently have an external origin that can be recognized, whereas in chronic spontaneous urticaria the trigger usually remains unknown. Even after ten years of follow-up in one cohort, no cause had been identified in about 45% of patients, while autoimmune disease, chronic infection and immune dysfunction were discovered in smaller fractions.

Infections are the most common identifiable cause of acute urticaria in children, and viruses account for most of the agents implicated. Some infection-associated urticaria appears to involve complement activation through immune complex formation. Parasites, Epstein–Barr virus, and hepatitis B and C are also listed among causes, and hepatitis C is linked to cryoglobulinemia. In chronic forms, intercurrent viral infections, typically of the upper respiratory tract, are a common cause of flares, and chronic low-grade infection can sometimes precede the onset of disease.

Drugs act through two distinct routes. Allergic reactions, mediated by IgE antibodies, are typically caused by beta-lactam antibiotics such as penicillin. Non-allergic reactions occur through direct mast cell degranulation, which is characteristic of aspirin, other NSAIDs, vancomycin and opiates. NSAID reactions are the best-studied example of pseudoallergic reactions: they are attributed to inhibition of COX-1, begin within minutes to a few hours, and resolve after the drug is stopped. NSAIDs can also trigger urticaria in a subset of patients who have chronic spontaneous urticaria, with reported flares in roughly 20–40% of such patients, although they do not usually provoke physical forms. A separate, single-drug allergic pattern of NSAID hypersensitivity also exists and must be distinguished from the pseudoallergic form.

Food is frequently suspected by patients, particularly in acute urticaria, where a majority of people name it as a cause, yet prospective studies rarely confirm this. True IgE-mediated food allergy accounts for less than 1% of reactions in adults, though it is more common in children. In chronic urticaria, food is rarely the cause and can usually be excluded by history. Where food matters, the culprit is more often a naturally occurring pseudoallergen, such as salicylates or biogenic amines (including histamine), or a food additive such as benzoates or tartrazine. Double-blind challenge studies have found that most reactions are linked to natural compounds rather than artificial additives. Diagnosis relies on a pseudoallergen-free diet, often for about three weeks, followed by provocation; in a subset of chronic patients, low-pseudoallergen diets have produced responses in more than half of those treated. The mechanism remains unclear, and a proposed role for reduced histamine-degrading enzyme activity has only been examined in small case series.

Stress and other emotional factors are regarded mainly as aggravating influences rather than primary causes. Fatigue, lack of sleep, menstruation, heat, tight clothing and alcohol are also reported to worsen symptoms. Patients with chronic urticaria report more life-event stress and perceived stress than people with allergic conditions, and psychological therapies are increasingly considered alongside medical treatment.

Chronic spontaneous urticaria is strongly associated with other autoimmune conditions, most often autoimmune thyroid disease. Reported rates of thyroid autoimmunity in patients vary widely, from about 6.5% to 57% across studies, and a systematic review found consistently raised levels of IgG antithyroid antibodies in CSU, with thyroid dysfunction more common in adults and in women. Patients with coexisting thyroid autoimmunity tend to have a more severe and prolonged course. Other conditions reported more often in chronic urticaria include rheumatoid arthritis, systemic lupus erythematosus, vitiligo, pernicious anemia, celiac disease and Sjögren's syndrome. The mechanisms linking these conditions are not fully established; one hypothesis proposes that thyroid disease worsens urticaria through complement activation. Atopic disease is also more frequent, particularly in adolescents, but IgE-mediated food allergy remains uncommon as a cause.

Several rare disorders can mimic or underlie chronic urticaria and should be considered when standard features do not fit. Hereditary angioedema results from deficiency or dysfunction of C1 inhibitor and causes recurrent swelling without typical itchy wheals, with little or no response to antihistamines. Systemic mastocytosis involves abnormal accumulation of mast cells in the skin and other organs, sometimes producing urticaria-like lesions. Urticarial vasculitis produces wheal-like lesions that last longer than 24 hours, often leaving bruising or pigmentation, and it is associated with systemic autoimmune disease. Recognizing these conditions is essential because their management differs substantially from that of ordinary urticaria.

Epidemiology and population burden

Estimates of how common urticaria is depend strongly on case definition, study design and region. Acute urticaria is the most frequent form, while the chronic forms, and CSU in particular, are harder to count. A 2020 systematic review and meta-analysis by Fricke and colleagues included 18 studies in its systematic evaluation and 11 in its meta-analysis, covering more than 86 million participants. Asian studies combined showed a higher point prevalence of chronic urticaria (1.4%) than those from Europe (0.5%) and Northern America (0.1%). The same review found that four studies that examined time trends indicated an increasing prevalence of chronic urticaria over time.

For CSU specifically, the global figures range widely. Depending on study design, the point prevalence of CSU varies from 0.02% to 2.7%. Within the United States, the picture depends on the data source. Insurance claim databases reported an estimated yearly prevalence of diagnosed CSU at 0.08%–0.11%, whereas a cross-sectional study using data from electronic health records reported a higher point prevalence of CSU at 0.23%. A survey-based analysis gave a higher weighted figure: among 74,994 respondents, 815 reported physician-diagnosed chronic urticaria, with 635 (77.9%) having CSU. Its weighted prevalence of diagnosed CSU was 0.78%. Claims-based work has also reported incidence rates, and the authors of one such study found a combined adult and paediatric point prevalence of about 0.28%. Because these studies use different case-finding methods, the differences are at least partly methodological.

Sex and age patterns

Women are more often affected in adult populations. In the pooled meta-analysis, women were slightly more affected than men, whereas in children < 15 years we did not find a sex-specific difference in the prevalence. In adult cohorts the imbalance is larger: women are almost twice as likely as men to develop the disease. A US adult population analysis reported that the standardized prevalence of CU among women was twice that of men.

Age patterns differ by form. Most patients with CSU are aged 20–40, and an incidence peak has been found in the third and fourth decades. Acute urticaria shows a different profile. Acute urticaria is common in children, affecting boys and girls equally. Across all ages, the lifetime burden of acute urticaria is substantial, with one review noting that 20% of the population having had it at some time. Among children, the incidence of all forms of urticaria varies between 2.1% and 6.7%, being more frequent in younger children. Chronic forms are rarer in this age group: one Portuguese cohort estimated that CU in children/adolescents occurs in only 0.1-0.3%, and a hospital-based study in children and adolescents reported a point prevalence of 0.16% (95% CI: 0.11-0.22).

Physical urticaria

Physical urticaria forms a substantial minority of chronic cases. One widely used clinical summary states that physical urticaria accounts for about 20% of cases. The share appears to be higher in children. In a comparative cohort of 193 patients with CSU or chronic inducible urticaria, in the pediatric group, chronic inducible urticaria (physical component), together with CSU, was observed in 7 (30.4%) patients. This was much greater than that in the adult group, which had only 16 patients (9.4%) with a physical component. Because the paediatric group in that study was small, these proportions should be treated as indicative rather than definitive.

Burden and health-care use

The burden of CSU is recognised mainly through its effects on quality of life. A narrative review found that itch was the primary and most troublesome symptom. CSU has a significant burden on physical and mental health-related quality of life (HRQoL). In children, the pattern is similar: chronic urticaria is substantially less common than acute urticaria but is associated with a larger decrease in quality of life. Data on health-care use and direct costs are less consistently reported than prevalence figures. Claims databases can count diagnosed cases and treatments, but the sources reviewed here did not provide a comparable, verified national cost estimate, so quantitative economic claims should be checked against specific population-level studies.

Diagnosis and differential diagnosis

History and symptom diary

Urticaria is diagnosed mainly on clinical grounds. The first step is a detailed history, the second a physical examination, and only for chronic disease a limited set of tests. The history should establish how long individual lesions last, how often they occur, and whether they follow exercise, heat, cold, pressure, or meals. It should also record recent drugs, particularly NSAIDs and ACE inhibitors, and any personal or family history of urticaria, angioedema, atopy, or autoimmune disease. Because wheals and angioedema are transient and are often absent during the visit, patients are asked to keep a diary and to photograph lesions. Guidelines also recommend asking about symptoms of anaphylaxis, which involve other organ systems and require urgent assessment. Activity and control are then tracked over time with standardized scores, such as the 7-day urticaria activity score and the angioedema activity score.

Laboratory testing

In acute urticaria, routine laboratory testing is generally not indicated, because most episodes resolve on their own and tests seldom change management. In chronic spontaneous urticaria (CSU), the EAACI/GA²LEN/EDF/WAO guideline limits the initial panel to a differential blood count, C-reactive protein and/or erythrocyte sedimentation rate, total IgE, and IgG anti-thyroid peroxidase antibodies, the last mainly in specialist care. Other tests are guided by clinical clues: stool examination for parasites when eosinophilia or relevant travel is present, antinuclear antibodies and rheumatoid factor when a rheumatic disorder is suspected, and hepatitis B and C serology when cryoglobulinemia or urticarial vasculitis is considered. Empiric elimination diets, extensive testing for inhalant or food IgE, and broad screening are not recommended, since routine testing rarely yields significant findings in patients whose history and examination show no atypical features.

Provocation tests and the autologous serum skin test

For chronic inducible urticaria (CIndU), provocation testing is the main confirmatory tool, and the guideline gives it strong consensus support. Threshold measurement is also used to follow disease activity. In heat urticaria, for example, successive five-minute challenges at temperatures between 45 °C and 36 °C are followed by an assessment of wheals and itch ten minutes later, and the lowest provoking temperature is recorded. Physical forms are otherwise confirmed with standardized stimuli, while allergy testing is reserved for cases with a specific allergic indication.

The autologous serum skin test (ASST) is an in vivo test in which the patient's own serum is injected intradermally. A weal-and-flare response suggests circulating histamine-releasing autoantibodies, usually directed at IgE or the high-affinity IgE receptor. Positive results are reported in roughly 40 to 45 percent of CSU patients, with one prospective series of 54 patients finding 40.7 percent. Accuracy estimates vary: one pooled estimate gives sensitivity near 70 percent and specificity of about 80 percent, whereas a smaller case-control study reported about 67 and 61 percent. Its negative predictive value is comparatively high, so a negative result argues against functional autoantibodies, but a positive result is only moderately specific, and the test is better regarded as a marker of autoreactivity than as proof of autoimmune urticaria. Preparation matters: antihistamines are withdrawn for at least two to three days beforehand, longer for doxepin and astemizole, and immunosuppressants are avoided for about two months. Serum-based ELISA and Western blot assays can detect antibodies, but they cannot tell functional from nonfunctional ones and are confined to specialist centres.

Biomarkers

No biomarker is validated for routine clinical use in urticaria. Current guidance allows additional markers to be assessed when appropriate, but none reliably establishes the diagnosis, predicts the course, or guides therapy. Clinical examination alone generally cannot separate autoimmune from nonautoimmune cases, which is why functional tests such as the ASST are still used selectively.

Differential diagnosis

The most important mimic is urticarial vasculitis, a small-vessel vasculitis with a characteristic time course. Individual lesions persist for more than 24 hours, often for days, and are typically 0.5 to 5 cm across. They tend to be painful or burning rather than itchy, and they heal with bruising or postinflammatory hyperpigmentation. Systemic features such as fever, arthralgia, and abdominal pain add weight to the diagnosis. Biopsy typically shows leukocytoclastic vasculitis. Consensus statements recommend a lesional skin biopsy when wheals last beyond 24 hours, when they resolve with residual bruising, or when systemic symptoms are present. Serum complement levels then separate normocomplementemic disease, which accounts for most cases, from hypocomplementemic disease, which is more often systemic and may involve anti-C1q antibodies.

Hereditary angioedema and other bradykinin-mediated angioedema must be excluded when swelling occurs without wheals, especially when there is a family history, the swelling is not itchy, and the patient does not respond to antihistamines. Guidelines single out angioedema without wheals as a feature that warrants further investigation. Systemic mastocytosis, in which clonal mast cells proliferate, should be considered when there are pigmented skin lesions, dermographism, or systemic symptoms, and it is usually investigated with serum tryptase measurement and, when indicated, bone marrow assessment. Other conditions to consider include lupus erythematosus tumidus, urticarial allergic contact dermatitis, Wells syndrome, and Schnitzler syndrome.

Treatment and management

Trigger avoidance and patient education

Care starts with identifying and avoiding triggers, and with teaching patients how the disease behaves. Where a specific trigger can be found, such as a drug, a physical stimulus or heat, removing it comes first. Clinicians also look for aggravating factors that are not triggers in themselves. Some evidence indicates that psychiatric conditions such as generalized anxiety disorder can worsen CSU through interactions among the nervous system, the immune system and the skin. In one reported case of refractory CSU with anxiety, cognitive behavioral therapy and escitalopram led to significant improvement, with complete resolution of symptoms within eight weeks. This is a single case, not a trial, but it illustrates why psychological assessment is part of management in persistent disease.

First-line antihistamines and up-dosing

Guidelines place second-generation H1-antihistamines as first-line therapy for all forms of urticaria. First-generation agents are not recommended as main treatment, although they may be used as adjuncts. If symptoms persist, a trial of up to a fourfold increase in the standard dose of a second-generation H1-antihistamine is suggested after two to four weeks, or sooner if symptoms are intolerable. Doses above fourfold are not recommended. The 2017 international guideline named several agents with evidence for higher doses, including cetirizine, desloratadine, fexofenadine, levocetirizine, bilastine, ebastine and rupatadine, and it did not endorse adding other drug classes at this step for lack of evidence.

Refractoriness is common. Estimates suggest that about 40-50% of patients with CSU will not respond to standard doses of H1-antihistamines. Up-dosing helps many of these patients, but not all. At least a quarter of patients with chronic urticaria have uncontrolled disease despite up-dosing of second-generation antihistamines.

Add-on and second-line therapy

For patients who remain symptomatic after high-dose antihistamines, the main option is omalizumab, a monoclonal anti-IgE antibody. The US approval covers patients aged 12 years and older who remain symptomatic despite H1-antihistamine treatment. The European licensed dose is 300 mg every four weeks, while the US label allows 150 mg or 300 mg. The guideline recommendation is to start with 300 mg every 4 weeks, based on placebo-controlled trials demonstrating efficacy in CSU. Dose escalation beyond the label is common in practice; real-world data suggest that up-dosing to 600 mg every 4 weeks, or 300 mg every 2 weeks, can benefit non-responders, though this is off-label. A randomized trial in antihistamine-refractory CSU with raised anti-thyroperoxidase IgE found that omalizumab produced a significantly larger reduction in weekly urticaria activity score than placebo.

Cyclosporine is the third step in the stepwise algorithm, given after omalizumab or alongside antihistamines. The evidence base includes eighteen studies with 909 participants, though only two of them were randomized controlled trials. Pooled response was modest at low to moderate doses: 54%, 66% and 73% at 4, 8 and 12 weeks. The main limitation is toxicity. Higher doses have been associated with side effects such as hypertension, peripheral neuropathy and raised serum creatinine in 20% to 30% of cases, and at lower doses adverse events are less frequent. Cyclosporine is not licensed for urticaria in most markets and is used off-label.

Newer agents are changing the picture. The US Food and Drug Administration has approved an oral BTK inhibitor, remibrutinib, for CSU, offering an alternative to injectable biologics such as omalizumab. Its approval rests on the Phase III REMIX-1 and REMIX-2 trials. The 2025 guideline also strongly suggests the use of dupilumab or remibrutinib as add-on treatment in patients with CSU who are unresponsive to high doses of second generation H1-antihistamines.

Emergency management of anaphylaxis and angioedema

Urticaria itself is rarely life-threatening, but swelling of the larynx, tongue or throat, or any sign of systemic anaphylaxis, requires immediate treatment. Intramuscular adrenaline (epinephrine) is the first-line drug in anaphylaxis and should not be delayed while antihistamines or corticosteroids are considered, since those are adjuncts only. Patients with breathing difficulty, low blood pressure or laryngeal swelling need emergency care and observation in hospital, because angioedema can progress after initial improvement. Patients with a history of severe reactions are typically prescribed an adrenaline auto-injector. Omalizumab is not a rescue treatment: it is not indicated for emergency treatment of allergic reactions, including anaphylaxis.

Note: The emergency-management paragraph is based on standard clinical practice and was not checked against a retrieved source.

Course, prognosis, and quality of life

Acute urticaria

Most acute episodes are short. Most cases of urticaria are self-limited and of short duration; the eruption rarely lasts more than several days, but it may be recurrent over weeks. Individual wheals are often gone within hours, and in childhood viral illnesses, urticarial eruptions which last a few weeks and then spontaneously subside are common. Prognosis is generally good. Acute urticaria is rarely fatal, the exception being angioedema involving the upper airways. Continued exposure to a known trigger can, however, cause the condition to become chronic. Estimates of how many acute cases progress vary; one source puts the figure at less than 40% becoming chronic urticaria, but this is a less rigorous source than the guidelines.

Chronic spontaneous urticaria

The course of CSU is much less predictable, and published figures differ considerably. The general view is that about one-third to one-half of patients with CSU will have remission of their disease within 1 year. Longer-term data are less consistent, with ongoing disease at five years estimated ranging from 15 to 70%. A UK clinical guidance document reports a different pattern, with remission rates of ~17% at 1 year, 50% at 5 years, and 73% at 20 years. Study populations also shape these numbers. One cohort reported a median duration of symptoms of nearly 4 years, and a study of children found remission rates that were low and are only about 10.3% per year.

Defining remission is itself difficult. The World Allergy Organization position paper notes that no evidence exists to propose any biomarkers for defining inflammatory or mechanistic remission in CSU or identifying patients with a high probability of cure. Relapse risk after a period of control was low in the studies reviewed, with the relapse rate of CSU remission, defined as 6 months, was low (range 3%-6.4%) after 12 months of follow-up. Among patients with severe disease treated with omalizumab, the same review reports a median remission rate of 47% (range 30%-68%) after 2 years.

Relapse after a full remission is well documented but variable. In a registry of 180 patients, in 23 (13%) patients, CSU was resolved during the first year. In 47 (26%) patients, CSU lasted more than 5 years. Recurrence occurred in 21% of our patients after having experienced a full remission anywhere between 1 to 10 years. Among those who relapsed, asthma, raised total IgE and thyroid autoantibodies were more common (asthma 40% versus 25% in the overall cohort; anti-thyroid peroxidase antibodies 44% versus 20%), which the authors linked to recurrence. These are single-centre, cross-sectional associations and should not be read as established predictors.

Factors linked to persistence

Several features have been associated with longer disease. Angioedema is believed to predict CSU disease duration and severity, and approximately two-thirds of patients with CSU report systemic complaints, including joint pain and fatigue. The registry data above link autoimmune features and high IgE with recurrence. Evidence that poor early response to treatment predicts a persistent course is weaker; a study of omalizumab response and relapse exists, but the available sources do not establish this association.

Quality of life, sleep, and mood

Quality of life is substantially affected. In a small Egyptian study of 25 patients with chronic urticaria, the mean of DLQI score was 24.8 indicating severe impact of QOL. A larger cohort found that 41.6% of patients with CSU had DLQI scores of 10 or greater. The domains most affected are symptoms and feelings, daily activities, work and school. Itch is a central driver: one study found that QOL is greatly influenced by itch intensity and disease activity, while the same study found no relationship with depression or anxiety.

Sleep is frequently disrupted. In a Spanish cross-sectional study of 75 patients, a majority of 59 of the patients suffered from poor sleep quality, and poor sleep was associated with higher rates of anxiety and depression. Depression and anxiety are the most common psychiatric findings in these patients; Choi et al. observed a prevalence 48.1% and 38.0% of depression and anxiety in Korean CU patients. The effects extend beyond the patient: in a small study, worse disease control and poorer quality of life in patients were associated with poorer family quality of life and higher rates of anxiety among the cohabitants.

Quality-of-life studies use several instruments. The Dermatology Life Quality Index (DLQI) is the most common, alongside the Urticaria Activity Score over seven days (UAS7), a visual analogue scale for itch, sleep questionnaires such as the PSQI, the Hospital Anxiety and Depression Scale, and the work productivity instrument WPAI-CU. Trial data have also used sleep-interference and activity-interference scores taken from daily diaries.

Research history and current directions

Early descriptions and naming

Written accounts of hives are very old. The Chinese medical text Huangdi Neijing is often cited as the earliest description, and it used the term "Feng Yin Zheng", meaning "wind-type concealed rash", for wheals that keep appearing, a term still the Chinese word for urticaria. In the West, Hippocrates described urticaria as a distinct disease entity and called it "knidosis" after the Greek word for nettles. The modern name comes from Latin urtica, meaning nettle, which is itself linked to urere, "to burn", a reference to the stinging sensation. The term "urticaria" was introduced in 1769 by William Cullen and adopted in 1792 by Johann Peter Frank.

An early clinical account with a wheal-and-flare picture appeared in 1794. Thomas Winterbottom, a physician in Sierra Leone, reported a woman who developed general swelling, especially of the face, after eating an unfamiliar wild fruit, with her nose hot, itchy and painful. He also noted that a similar eruption followed many substances taken orally, which the local population called a "surfeit".

Mast cells, histamine and IgE

Mast cells were first identified by Paul Ehrlich in 1878, when he was still a medical student. Working with aniline stains, Ehrlich described granular cells in connective tissue and named them Mastzellen. The name rested on a mistaken idea about where the granules came from, and the cells were for decades regarded mainly as sources of tissue nourishment. The function of mast cells remained elusive until the 1950s, when studies established them as the main storage site for histamine. Histamine itself had been named earlier: in the early 1900s, Dale and Laidlaw isolated an amine from tissue that acted on smooth muscle and blood vessels. Later work linked mast cells, histamine and anaphylaxis, showing that histamine was present in mast cells and was released with heparin during anaphylactic shock. Sources differ on the date of Ehrlich's discovery; some give 1879 rather than 1878.

The role of IgE came later. Renewed interest followed the discovery of IgE in 1967 by Kimishige Ishizaka. Ishizaka's group showed that IgE is essential for histamine release from mast cells, a finding that became a foundation of allergy research. Today, IgE binds the high-affinity FcεRI receptor on mast cells, and antigen cross-linking of bound IgE triggers degranulation.

Anti-IgE therapy and the omalizumab trials

If IgE drives mast cell activation, blocking IgE might also relieve urticaria. Omalizumab, a humanised anti-IgE monoclonal antibody, was first approved for allergic asthma and was then tested in chronic urticaria. Large multicenter, randomized, double-blind, placebo-controlled phase III trials (ASTERIA I, ASTERIA II, and GLACIAL) showed that omalizumab significantly improved outcomes compared with placebo in patients with CSU. ASTERIA II, presented in February 2013, enrolled 323 patients with a history of at least 6 months of chronic idiopathic urticaria, with itchy hives for at least 8 consecutive weeks despite H1-antihistamines. The 150 mg and 300 mg doses met the primary endpoint, while the 75 mg dose did not reach statistical significance. In a post hoc analysis, 53% of patients receiving the high dose were completely free of hives at the end of treatment, compared with 10% in the placebo group. GLACIAL recruited patients whose symptoms persisted despite antihistamines up to four times the approved dose. A later pooled analysis concluded that the 300 mg dose had similar effectiveness regardless of current urticaria background therapy. Regulatory approval for chronic spontaneous urticaria followed in the United States in 2014.

Anti-IgE treatment is not effective for every patient. Some people with CSU respond poorly, and the reasons are still under study, which links to the open questions on mast cell activation discussed elsewhere in this entry.

Guidelines and newer targeted therapies

Consensus guidelines from European and international allergy and dermatology organisations have been revised several times since the first edition, and each revision has refined definitions and classification, including the replacement of "idiopathic" by "spontaneous". Current research is testing agents that act on other points in the mast cell pathway or on the wider immune system. These include antibodies against the mast cell receptor KIT, inhibitors of Bruton's tyrosine kinase, which affects mast cell and B cell signalling, and biologics targeting type 2 cytokine pathways. Some of these are in late-stage trials, and their place in routine practice is still being defined.

Open questions and controversies

What activates mast cells in most CSU cases

Autoimmunity explains only part of chronic spontaneous urticaria (CSU). Type IIb disease, defined by IgG autoantibodies against IgE or its receptor, is found in fewer than one in ten patients when a strict definition requires three concordant tests: the autologous serum skin test, IgG immunoassays and the basophil activation test is present in less than 10% of patients with CSU when strict criteria are used. Many patients therefore have no identifiable trigger for their mast cells. Researchers are examining routes that bypass IgE and IgG altogether, which involve a variety of endogenous danger signals and intrinsic cellular dysregulation. Candidate activating receptors include MRGPRX2, the C5a receptor and protease-activated receptors 1 and 2 (other activating receptors, including Mas-related G-protein–coupled receptor-X2, C5a receptor, and protease-activated receptors 1 and 2 are responsible for MC activation). Coagulation is another line of inquiry. Markers of coagulation activation appear in roughly half of severe cases, and those patients often respond poorly to antihistamines and cyclosporine. One proposal is that autoantigens expressed only in the skin keep IgE-driven reactions local, which might partly explain why systemic mast cell activation is uncommon (Expression of autoantigens only in the skin might explain why IgE autoantibodies and their autoallergens, in patients with CSU, interact primarily in the skin). This remains a hypothesis.

Biomarkers for activity, duration and treatment response

No laboratory test currently serves as a diagnostic biomarker for CSU. A diagnostic biomarker for CSU is still missing. Most biomarkers described so far do not seem to possess sufficient specificity for this disease. Several candidates have been studied for monitoring rather than diagnosis. Basopenia has been proposed as a sensitive marker of activity, but the evidence is considered insufficient for routine use (Basopenia has been suggested as a specific and sensitive biomarker of CSU activity, but information is currently insufficient to consider its routine clinical use.). Total IgE shows a signal with disease duration: elevated levels were seen in 40% of patients whose disease had lasted over 25 months, compared with 23% of those with shorter courses. In a 44-patient study, CRP and D-dimer separated patients from controls but did not track activity, whereas C4 correlated with activity (There was no correlation between PT, aPTT, D-dimer, CRP, C3 and disease activity.). Predicting response to omalizumab has also produced conflicting results. A single-centre study did not confirm the usefulness of SII, SIRI, NLR or PLR as predictors of the response to OMA in CSU. By contrast, a review identified high baseline disease burden and raised CRP and D-dimer among predictors of response to second-generation antihistamine treatment (a high baseline 7-day urticaria activity score or a low baseline urticaria control test score—along with elevated CRP and D-dimer levels). Clinicians still rely on the seven-day urticaria activity score (UAS7), which assesses the key sign (hives) and symptom (itch) of CSU.

Neuroimmune links and the psychological burden

The proposed link between the brain and mast cells rests mainly on stress biology. During psychological stress, released stress hormones and neuropeptides (e.g., CRH and substance P) bind to mast cell receptors and stimulate them to release their mediators. Reviews also describe neuroinflammation in regions tied to mood, such as the prefrontal cortex, cerebellum and thalamus (Involvement of the CNS may affect brain regions like the prefrontal cortex, cerebellum, and thalamus which are involved in anxiety and depression.), but these claims come largely from narrative reviews. The causal role of stress is unsettled: the role of psychological factors in development and aggravation is not fully confirmed, and it is still poorly understood how psychological stress interferes with the skin immune system in CSU. Itch may also feed back into mood. Scratching further activates reward pathways in the central nervous system (CNS), reinforcing compulsive scratching behavior. Psychiatric comorbidity is reported frequently. One study found that common conditions include anxiety (30.6%), depression (29.4%), and sleep-wake disorders (36.7%). Whether these conditions drive the disease, follow from it, or both, is not yet resolved, and whether immune signalling reaches the brain in a susceptible subgroup remains a open question.

Testing, classification and overlapping forms

Experts disagree on how far laboratory work-up should go in CSU. Assays that detect functional autoantibodies are still largely research tools. One proof-of-concept study of 43 patients reported that CD63 response on NS-LAD2 was significantly increased in CSU patients compared to controls, but validation in wider settings is still needed. Classification is also contested. Type I and type IIb mechanisms coexistence in some patients, and one analysis concluded that two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU. Some endotype schemes therefore include separate categories for concomitant type I and type IIb disease and for patients who fit neither, an approach that Type I, Type IIb, Concomitant Type I/Type IIb, and Non-Type I/Type IIb Chronic Spontaneous Urticaria reflects. Until shared criteria and validated biomarkers exist, comparisons between studies and decisions about testing will remain difficult.

References

1. Urticaria and Angioedema - an overviewsciencedirect.com
2. Urticaria: A Narrative Overview of Differential Diagnosis - PMCpmc.ncbi.nlm.nih.gov
3. Differential Diagnosis of Urticarial Lesionsncbi.nlm.nih.gov
4. Urticaria - an overviewsciencedirect.com
5. Urticaria and Angioedema: A Practical Approachaafp.org
6. Treatment of Idiopathic Angioedema With Xolair as Add-on Therapycdn.clinicaltrials.gov
7. Angioedema: Causes, Appearance and Treatment — DermNetdermnetnz.org
8. Angio-oedema: Causes, Symptoms, and Treatmentpatient.info
9. Angioedema - StatPearls - NCBI Bookshelfncbi.nlm.nih.gov
10. Urticaria: recommendations from the Italian Society of Allergology, Asthma and Clinical Immunology and the Italian Society of Allergological, Occupational and Environmental Dermatologyncbi.nlm.nih.gov
11. Urticaria and Angioedemaunboundmedicine.com
12. Angioedema - Allergy and Immunology - Merck Manual Professional Editionmerckmanuals.com
13. Chronic Urticaria and Angioedema: Masqueraders and Misdiagnoses - ScienceDirectsciencedirect.com
14. What is Angioedema?news-medical.net
15. (PDF) The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticariaresearchgate.net
16. Chronic Spontaneous Urticariae-aair.org
17. Relationship of Acute and Chronic Urticaria: A Spectrum Disease or Two Different Entities? Relationship of Acute and Chronic Urticarialink.springer.com
18. The safety and tolerability profile of bilastine for chronic urticaria in childrenncbi.nlm.nih.gov
19. Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history - UpToDateuptodate.com
20. Methods of treating chronic spontaneous urticaria using a bruton's tyrosine kinase inhibitorimage-ppubs.uspto.gov
21. A Safety Extension Study to Evaluate the Long-term Safety of QGE031 in Chronic Spontaneous Urticaria (CSU) Patientscdn.clinicaltrials.gov
22. Chronic urticaria: profile from a reference centerncbi.nlm.nih.gov
23. Chronic spontaneous urticariadermnetnz.org
24. Urticaria: chronic spontaneous urticaria (chronic ordinary urticaria; chronic idiopathic urticaria)pcds.org.uk
25. The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria - Zuberbier - 2022 - Allergy - Wiley Online Libraryonlinelibrary.wiley.com
26. Diagnosis and Management of Urticaria in Indian Settings: Skin Allergy Research Society's Guideline-2022 - PMCpmc.ncbi.nlm.nih.gov
27. To Compare Efficacy and Safety of CT-P39 and EU-approved Xolair in Patients With Chronic Spontaneous Urticariacdn.clinicaltrials.gov
28. Advances in Understanding and Managing Chronic Urticariancbi.nlm.nih.gov
29. Chronic spontaneous urticaria and chronic inducible urticaria - Journal of Allergy and Clinical Immunologyjacionline.org
30. Urticaria - Kaplan AP (Updated 2019)worldallergy.org
31. (PDF) Chronic inducible urticaria: classification and prominent features of physical and non-physical typesresearchgate.net
32. Chronic Urticaria—Pathogenesis, Diagnostics, Therapy and Influence of Coexisting Angioedema - PMCpmc.ncbi.nlm.nih.gov
33. Chronic Inducible Urticaria Part Iintechopen.com
34. URTICARIA DIAGNOSISemjreviews.com
35. Cholinergic Urticaria - an overviewsciencedirect.com
36. Chronic inducible urticariadermnetnz.org
37. Cholinergic Urticaria: Background, Epidemiology, Etiologyemedicine.medscape.com
38. Cholinergic Urticaria with Anaphylaxis: An Underrecognized Clinical Entity - The Journal of Allergy and Clinical Immunology: In Practicejaci-inpractice.org
39. Chronic inducible urticaria: A systematic review of treatment options - Journal of Allergy and Clinical Immunologyjacionline.org
40. Pathogenesis of Physical Induced Urticarial Syndromesclinicaltrials.gov
41. Acute and Chronic Urticaria Diagnosis and Management Taking into Account Their Differenceslink.springer.com
42. Mechanisms of histamine release from mast cells beyond the high affinity IgE receptor in severe chronic spontaneous urticaria - ScienceDirectsciencedirect.com
43. Frontiersfrontiersin.org
44. Chronic urticaria and the pathogenic role of mast cells - ScienceDirectsciencedirect.com
45. Mast cell signaling and its role in urticaria - Annals of Allergy, Asthma & Immunologyannallergy.org
46. Current Concepts in the Pathogenesis and Management of ...bahrainmedicalbulletin.com
47. Urticaria. An updated review - PubMedpubmed.ncbi.nlm.nih.gov
48. Emerging Therapies in Chronic Spontaneous Urticariae-aair.org
49. Chronic spontaneous urticaria: update on pathogenesis and therapeutic implications - PMCpmc.ncbi.nlm.nih.gov
50. Severe chronic spontaneous urticaria responding and not responding to omalizumab: analysis of the prognostic value of known and novel in-vitro variables - PubMedpubmed.ncbi.nlm.nih.gov
51. Elevated, FcεRI-Dependent MRGPRX2 Expression on Basophils in Chronic Urticariaacademic.oup.com
52. Remibrutinib inhibits hives effector cells stimulated by serum from chronic urticaria patients independently of FcεR1 expression level and omalizumab clinical responsencbi.nlm.nih.gov
53. Response of FcεRI‐bearing leucocytes to omalizumab in chronic spontaneous urticaria - PMCpmc.ncbi.nlm.nih.gov
54. Omalizumab for Patients with Chronic Spontaneous Urticaria: A Narrative Review of Current Statuslink.springer.com
55. Treatment approaches for omalizumab-refractory chronic spontaneous urtdovepress.com
56. Endotypes of chronic spontaneous urticaria and angioedema - Journal of Allergy and Clinical Immunologyjacionline.org
57. The Role of Coagulation and Complement Factors for Mast Cell Activation in the Pathogenesis of Chronic Spontaneous Urticariadoi.org
58. Chronic Spontaneous Urticaria: The Role and Relevance of Autoreactivity, Autoimmunity, and Autoallergy - ScienceDirectsciencedirect.com
59. Autoimmune chronic spontaneous urticaria - Journal of Allergy and Clinical Immunologyjacionline.org
60. Clinical and molecular aspects of managing chronic spontaneous urticaria: identifying endotypes, phenotypes, and determinants of treatment response and resistance - PMCpmc.ncbi.nlm.nih.gov
61. Treatment Approaches for Omalizumab-Refractory Chronic Spontaneous Urticaria - PMCpmc.ncbi.nlm.nih.gov
62. Chronic spontaneous urticaria and the extrinsic coagulation system - ScienceDirectsciencedirect.com
63. Beyond the itch: the complex interplay of immune, neurological, and psychological factors in chronic urticarialink.springer.com
64. Enhanced thrombin generation potential and endothelial dysfunction in chronic spontaneous urticariancbi.nlm.nih.gov
65. Type I and type IIb autoimmune chronic spontaneous urticaria: Using common clinical tools for endotyping patients with CSU - ScienceDirectsciencedirect.com
66. Most Patients With Autoimmune Chronic Spontaneous Urticaria Also Have Autoallergic Urticaria, but Not Vice Versa - ScienceDirectsciencedirect.com
67. Towards Personalised Therapy in Chronic Spontaneous Urticaria: Advancing From Endotype to Clinical Responsencbi.nlm.nih.gov
68. Thyroid Autoimmunity in CSU: A Potential Marker of Omalizumab Response? - PMCncbi.nlm.nih.gov
69. Frontiersfrontiersin.org
70. The Role of Coagulation and Complement Factors for Mast Cell Activation in the Pathogenesis of Chronic Spontaneous Urticariamdpi.com
71. Pseudoallergy - an overviewsciencedirect.com
72. Acute and Chronic Urticaria: Evaluation and Treatmentaafp.org
73. BSACI guideline for the management of chronic urticaria ...bsaci.org
74. The role of allergens and pseudoallergens in urticaria - PubMedpubmed.ncbi.nlm.nih.gov
75. PD31 - Pseudoallergic reactions to food and drugs in children with chronic idiopathic urticariancbi.nlm.nih.gov
76. Stress, pseudoallergens, autoimmunity, infection and inflammation in chronic spontaneous urticariancbi.nlm.nih.gov
77. Allergic Urticaria - an overviewsciencedirect.com
78. Navigating NSAID hypersensitivity: a phenotype-based algorithm for diagnosis and safe therapylink.springer.com
79. Chronic urticaria and thyroid autoimmunity: a perplexing associationacademic.oup.com
80. Comorbidity of chronic spontaneous urticaria and autoimmune thyroid diseases: A systematic review - Kolkhir - 2017 - Allergy - Wiley Online Libraryonlinelibrary.wiley.com
81. Chronic Urticaria (Hives) and Autoimmunityskintherapyletter.com
82. Open Access Chronic urticaria and thyroid pathologyworldallergyorganizationjournal.org
83. Prevalence of chronic urticaria in children and adults across the globe: Systematic review with meta‐analysis - Fricke - 2020 - Allergy - Wiley Online Libraryonlinelibrary.wiley.com
84. Clinical profile, prevalence, and burden of chronic spontaneous urticaria in the United States - World Allergy Organization Journalworldallergyorganizationjournal.org
85. Clinical profile, prevalence, and burden of chronic spontaneous urticaria in the United States - PMCpmc.ncbi.nlm.nih.gov
86. Frontiersfrontiersin.org
87. Prevalence estimates for chronic urticaria in the United States: A sex- and age-adjusted population analysis - ScienceDirectsciencedirect.com
88. Epidemiological and Clinical Characteristics of Adult and Pediatric Patients with Chronic Spontaneous Urticariancbi.nlm.nih.gov
89. [Chronic urticaria. Prevalence, course, prognostic factors and impact] - PubMedpubmed.ncbi.nlm.nih.gov
90. Urticaria and other mimickers of urticariancbi.nlm.nih.gov
91. Urticaria in a Pediatric Population: A Portuguese Single-Center Cohort Reportncbi.nlm.nih.gov
92. Prevalence of chronic urticaria: A study in the pediatric population of a general hospital - PubMedpubmed.ncbi.nlm.nih.gov
93. Chronic Urticaria: Background, Epidemiology, Etiologyemedicine.medscape.com
94. Epidemiological and Clinical Characteristics of Adult and Pediatric Patients with Chronic Spontaneous Urticaria - PMCpmc.ncbi.nlm.nih.gov
95. The Burden of Chronic Spontaneous Urticaria: A Narrative Literature Review - PubMedpubmed.ncbi.nlm.nih.gov
96. Chronic Urticaria in Children: A Reviewemjreviews.com
97. Incidence and Prevalence of Chronic Spontaneous Urticaria Among Adult and Pediatric Populations in the United Stateslink.springer.com
98. Pathophysiology, Diagnosis, and Management of Chronic Spontaneous Urticaria: A Literature Review - PubMedpubmed.ncbi.nlm.nih.gov
99. AAAAI/ACAAI Diagnosis and Management of Acute and Chronic Urticaria Guideline Summary - Guideline Centralguidelinecentral.com
100. Urticaria Workup: Approach Considerations, Laboratory Studies, Imaging Studiesemedicine.medscape.com
101. Chronic Urticaria Workup: Approach Considerations, Laboratory Studies, Provocation and Allergy Testingemedicine.medscape.com
102. Urticaria Diagnosis & Treatment Guidelines Update - Dermatology Advisordermatologyadvisor.com
103. Urticaria: EAACI/GA²LEN/EDF/APAAACI 2021 Guideline Summaryreference.medscape.com
104. Diagnostic testing for chronic spontaneous urticaria with or without angioedema: The do's, don't and maybe's - World Allergy Organization Journalworldallergyorganizationjournal.org
105. Acute and Chronic Urticaria: Evaluation and Treatmentaafp.org
106. Diagnosis of urticaria : Indian Journal of Dermatologyovid.com
107. Autologous Serum Skin Test as a Diagnostic Aid in Chronic Idiopathic Urticariancbi.nlm.nih.gov
108. Usefulness of the Autologous Serum Test for the Diagnosis of Chronic Idiopathic Urticaria - PMCpmc.ncbi.nlm.nih.gov
109. AUTOLOGOUS SERUM SKIN TEST - PMC - NIHpmc.ncbi.nlm.nih.gov
110. Autologous Serum Skin Testworldallergy.org
111. 35 years of autologous serum skin test in chronic ...eurannallergyimm.com
112. Urticarial vasculitis: Clinical and laboratory findings with a particular emphasis on differential diagnosis - Journal of Allergy and Clinical Immunologyjacionline.org
113. Urticarial Vasculitisdermatologyadvisor.com
114. Differential diagnosis between urticarial vasculitis and chronic spontaneous urticaria: An international Delphi survey - PMCpmc.ncbi.nlm.nih.gov
115. Hypocomplementemic Urticarial Vasculitis: A Case Reportncbi.nlm.nih.gov
116. Urticarial Vasculitis: Practice Essentials, Pathophysiology, Etiologyemedicine.medscape.com
117. Mental Health Interventions in Refractory Chronic Spontaneous Urticaria: A Call to Expand Treatment Guidelinesncbi.nlm.nih.gov
118. Updated Urticaria Guidelines Clarify Diagnosis, Biomarkers, Treatment Pathwayshcplive.com
119. Chronic Urticaria: Following Practice Guidelinesskintherapyletter.com
120. Chronic urticaria guidelines updateddermatologytimes.com
121. Chronic urticaria: unmet needs, emerging drugs, and new perspectives on personalised treatment - The Lancetthelancet.com
122. Novartis Announces FDA Approval of Xolair® (omalizumab) for Chronic Idiopathic Urticaria (CIU), a Form of Chronic Hivesnovartis.com
123. Chronic spontaneous urticaria guidelines: What is new? - Journal of Allergy and Clinical Immunologyjacionline.org
124. Management of Chronic Spontaneous Urticaria Made Practical: What Every Clinician Should Know - ScienceDirectsciencedirect.com
125. Cyclosporine for Chronic Spontaneous Urticaria: A Meta-Analysis and Systematic Review - The Journal of Allergy and Clinical Immunology: In Practicejaci-inpractice.org
126. Low-dose cyclosporine is a good option for severe chronic urticaria - Journal of Allergy and Clinical Immunologyjacionline.org
127. A new era in chronic spontaneous urticaria: FDA approval of the oral BTK inhibitor remibrutinibncbi.nlm.nih.gov
128. Omalizumab - StatPearls - NCBI Bookshelfncbi.nlm.nih.gov
129. Omalizumab Updosing in Chronic Spontaneous Urticaria: an Overview of Real-World Evidencelink.springer.com
130. Acute Urticaria: Background, Etiology, Pathophysiologyemedicine.medscape.com
131. Urticaria (Hives): Causes, Symptoms, Treatmentsmedparkhospital.com
132. Natural history, prognostic factors and patient perceived response to treatment in chronic spontaneous urticarialink.springer.com
133. Natural history, prognostic factors and patient perceived response to treatment in chronic spontaneous urticariaaacijournal.biomedcentral.com
134. Chronic spontaneous urticaria remission definition and therapy stepping down: World Allergy Organization position paper - Journal of Allergy and Clinical Immunologyjacionline.org
135. Predictive features associated with chronic spontaneous urticaria recurrence - PubMedpubmed.ncbi.nlm.nih.gov
136. A Practical Approach to Diagnosing and Managing Chronic Spontaneous Urticarialink.springer.com
137. Does chronic urticaria affect quality of sleep and quality of life? - PubMedpubmed.ncbi.nlm.nih.gov
138. Does chronic urticaria affect quality of sleep and quality of life? - PMCpmc.ncbi.nlm.nih.gov
139. Sleep Quality as a Predictor of Quality-of-Life and Emotional Status Impairment in Patients with Chronic Spontaneous Urticaria: A Cross-Sectional Studyncbi.nlm.nih.gov
140. Does chronic urticaria affect quality of sleep and quality of life? - Azza M Abdel-Meguid, Sara M Awad, Mostafa Noaman, Asmaa M Abdel Gawad, Doaa A E Abou-Taleb, 2024journals.sagepub.com
141. The Burden on Cohabitants of Patients with Chronic Spontaneous Urticaria: A Cross-Sectional Studyncbi.nlm.nih.gov
142. Clinical Practice Guidelines : Urticariarch.org.au
143. Why a Complete Response Is the Treatment Aim in Chronic Spontaneous Urticariancbi.nlm.nih.gov
144. Ligelizumab improves sleep interference and disease burden in patients with chronic spontaneous urticariancbi.nlm.nih.gov
145. Quality of Life in Patients With Chronic Urticariaclinicaltrials.gov
146. Historyurtikaria.net
147. The Discovery of Mast Cells: An Historical Note - PubMedpubmed.ncbi.nlm.nih.gov
148. Mast Cells - Characterization, Markers and Antibodiesbio-rad-antibodies.com
149. Editorial: Mast cells in allergic diseasesncbi.nlm.nih.gov
150. Omalizumab in Chronic Spontaneous Urticaria Refractory to Conventional Therapy: An Italian Retrospective Clinical Analysis with Suggestions for Long-Term Maintenance Strategies - PMCpmc.ncbi.nlm.nih.gov
151. ASTERIA II: Omalizumab Calms Itch in Chronic Urticariamedscape.com
152. Efficacy Of Omalizumab In Patients With Chronic Idiopathic/Spontaneous Urticaria With Different Background Therapy: Post Hoc Analysis Of Asteria I, Asteria II, and Glacial Studies - Journal of Allergy and Clinical Immunologyjacionline.org
153. The Definition, Classification, and History of Urticaria - ScienceDirectsciencedirect.com
154. Urticaria - Etymology, Origin & Meaningetymonline.com
155. Cases of the Urticaria or Nettle Rash, with Observations: Communicated in a Letter to Robert Willan, M. D. Physician in London, and by Him to Dr. Simmonsncbi.nlm.nih.gov
156. Frontiersfrontiersin.org
157. Journal of Histochemistry & Cytochemistry 2014, Vol. 62(10) 698­–738scienceopen.com
158. Paul Ehrlich's doctoral thesis: A milestone in the study of mast cellsresearchgate.net
159. Kimishige Ishizakaen.wikipedia.org
160. Definitionucare-4u.com
161. The role of mast cells in allergic inflammation - ScienceDirectsciencedirect.com
162. Key clinical-trial evidence for omalizumabdermnetnz.org
163. Novartis Reports Omalizumab Significantly Improved Chronic Idiopathic Urticaria Symptoms in Patients Who Failed Standard Therapynovartis.com
164. Frontiersfrontiersin.org
165. Biomarkers of chronic spontaneous urticaria and their clinical implications: Expert Review of Clinical Immunology: Vol 17 , No 3 - Get Accessdoi.org
166. Biomarkers of disease activity in patients with chronic spontaneous urticaria - PubMedpubmed.ncbi.nlm.nih.gov
167. Chronic Urticaria Treatment with Omalizumab—Verification of NLR, PLR, SIRI and SII as Biomarkers and Predictors of Treatment Efficacyncbi.nlm.nih.gov
168. Biomarkers in Chronic Spontaneous Urticaria: Are We Ready for its Use in Clinical Practice?link.springer.com
169. Association Between Proinflammatory Cytokines IL-6 and TNF-Alpha, Psychological Stress and Chronic Spontaneous Urticaria Severityncbi.nlm.nih.gov
170. The Neuropsychological Dimensions to Pathogenesis of Chronic Spontaneous Urticaria Beyond Autoallergypmc.ncbi.nlm.nih.gov
171. (PDF) Neuro–Immuno–Psychological Aspects of Chronic Urticariaresearchgate.net
172. The Neuropsychological Dimensions to Pathogenesis of Chronic Spontaneous Urticaria Beyond Autoallergyovid.com
173. Autoimmune Mast Cell Activation Test as a Diagnostic Tool in Chronic Spontaneous Urticariancbi.nlm.nih.gov
174. Endotypes, phenotypes, and biomarkers in chronic spontaneous urticaria: Evolving toward personalized medicine - ScienceDirectsciencedirect.com