Urticaria
Urticaria, commonly known as hives, is a heterogeneous group of disorders characterized by the sudden appearance of transient, pruritic, erythematous wheals and/or angioedema. The pathogenesis of urticaria primarily involves the activation and degranulation of cutaneous mast cells, resulting in the release of histamine and other pro-inflammatory mediators that increase vascular permeability and vasodilation, leading to the clinical manifestations. Immunological mechanisms, such as IgE-mediated hypersensitivity, autoimmune reactions, or direct mast cell activation, are implicated depending on the subtype. Urticaria can be acute or chronic, with chronic forms persisting for six weeks or longer. The health impacts of urticaria are significant, including intense itching, discomfort, sleep disturbance, and impaired quality of life. In severe cases, angioedema may compromise the airway, posing a life-threatening risk.
Acute urticaria is defined by the sudden onset of wheals, angioedema, or both, lasting less than six weeks. It is often triggered by allergens such as foods, medications, or infections, and typically resolves spontaneously or with short-term therapy. The lesions are transient, usually disappearing within 24 hours without residual skin changes.
Chronic spontaneous urticaria (CSU) is characterized by the spontaneous appearance of wheals, angioedema, or both, persisting for six weeks or longer without an identifiable external trigger. The etiology is often idiopathic, but autoimmune mechanisms, including autoantibodies against the high-affinity IgE receptor or IgE itself, are implicated in a substantial subset of cases. Symptoms fluctuate in intensity and frequency, often severely impacting quality of life.
Chronic inducible urticaria encompasses forms of urticaria that are reproducibly triggered by specific physical or environmental stimuli, such as pressure, cold, heat, sunlight, vibration, or water. Each subtype is defined by its unique trigger and pathophysiology. Symptoms persist for six weeks or longer and may overlap with chronic spontaneous urticaria.
Angioedema involves deeper swelling of the skin and mucosa, often affecting the eyelids, lips, tongue, and sometimes the larynx or gastrointestinal tract. It may occur with or without wheals and is mediated by similar mast cell-derived mediators as urticaria, although bradykinin-mediated forms exist. Angioedema can be acute or chronic and may have life-threatening implications if the airway is involved.
Urticaria is a common dermatological disorder affecting individuals of all ages, with a lifetime prevalence estimated at 15–20%. Acute urticaria is more frequent in children and young adults, whereas chronic urticaria predominantly affects adults, with a peak incidence between the third and fifth decades of life. Chronic urticaria has a point prevalence of approximately 0.5–1% in the general population. Women are affected about twice as often as men, particularly in chronic forms. Geographic and ethnic variations exist, but the disease is reported worldwide. The burden of disease is substantial due to recurrent symptoms, impact on daily activities, sleep, and psychological well-being. While most cases of acute urticaria resolve within days to weeks, chronic urticaria can persist for months or years, with spontaneous remission rates of 30–50% within one year and up to 70% within five years.
The diagnosis of urticaria is primarily clinical, based on the history and physical examination. Key diagnostic features include the presence of transient, pruritic wheals and/or angioedema, typically resolving within 24 hours without residual skin changes. A detailed history should assess the duration, frequency, and pattern of symptoms, potential triggers, associated systemic symptoms, family history, and medication use. For acute urticaria, identification of potential allergens or recent infections is essential. In chronic urticaria, an assessment for inducible triggers and possible autoimmune or systemic diseases is warranted. Routine laboratory testing is generally not required for acute urticaria unless systemic illness is suspected; however, in chronic cases, basic investigations such as complete blood count, erythrocyte sedimentation rate, C-reactive protein, and thyroid function tests may be indicated to exclude underlying causes. Provocation tests can be performed for inducible urticaria subtypes. Skin biopsy is rarely needed, reserved for atypical presentations or suspicion of urticarial vasculitis. Diagnostic criteria emphasize the recurrent nature of wheals and/or angioedema, their transient nature, and exclusion of other dermatoses.
Treatment options for urticaria include several pharmacological agents. Dupilumab is a monoclonal antibody that targets the interleukin-4 receptor alpha, modulating type 2 inflammation pathways. Bilastine is a non-sedating second-generation antihistamine used for symptomatic relief of urticaria. Omalizumab, a monoclonal antibody against IgE, is indicated for chronic spontaneous urticaria refractory to antihistamines. Rupatadine fumarate is a second-generation antihistamine with additional platelet-activating factor antagonist properties, effective in managing urticaria symptoms. Levocetirizine dihydrochloride, the active enantiomer of cetirizine, is a potent, non-sedating antihistamine used for symptomatic treatment. Desloratadine is another second-generation antihistamine, offering relief from pruritus and wheals. Bepotastine besilate is an antihistamine with additional anti-inflammatory actions, indicated for urticaria. Mizolastine is a non-sedating antihistamine used to alleviate symptoms of urticaria. Olopatadine hydrochloride acts as a selective histamine H1 antagonist and stabilizes mast cells, providing symptomatic control. Fexofenadine hydrochloride is a non-sedating H1 antihistamine commonly prescribed for urticaria to reduce itching and wheal formation.
| Structure | Generic Name | CAS Registry Number | Molecular Formula | Molecular Weight |
|---|---|---|---|---|
| dupilumab (Rec INN; USAN); duplimab | 1190264-60-8 | |||
 | bilastine (Rec INN) | 202189-78-4 | C28 H37 N3 O3 | 463.612 |
| omalizumab (Rec INN; USAN) | 242138-07-4 | |||
 | rupatadine fumarate (Prop INNM) | 158876-82-5 (free base); 182349-12-8 | C26 H26 Cl N3 . C4 H4 O4 | 532.03 |
 | (-)-cetirizine dihydrochloride; levocetirizine dihydrochloride (Prop INNM; USAN) | 130018-77-8 (free base); 130018-87-0 | C21 H25 Cl N2 O3 . 2 Cl H | 461.81 |
 | descarboethoxyloratadine; desloratadine (Prop INN; USAN) | 100643-71-8 | C19 H19 Cl N2 | 310.821 |
 | bepotastine besilate (Prop INNM; USAN) | 190786-44-8 | C21 H25 Cl N2 O3 . C6 H6 O3 S | 547.063 |
 | mizolastine (Rec INN; BAN) | 108612-45-9 | C24 H25 F N6 O | 432.493 |
 | olopatadine hydrochloride (Rec INNM; USAN) | 113806-05-6 (free base); 140462-76-6 | C21 H23 N O3 . Cl H | 373.873 |
 | fexofenadine hydrochloride (Prop INNM; USAN; BANM); terfenadine carboxylate hydrochloride | 153439-40-8 | C32 H39 N O4 . Cl H | 538.117 |
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