Urticaria, also known as welts, hives, or wheals, is characterized by the appearance of intensely pruritic erythematous plaques. It appears clinically as pruritic, pale, blanching swellings of the superficial dermis that last for up to 24 hours. Lesions may be small, large, giant, oval, or annular.
Urticaria affects 10% to 25% of the population and can occur in any age group. It is a mast-cell-driven disease. The triggering mechanisms for mast-cell activation in urticaria are not well defined but seem to be multiple and diverse. Urticaria is classified according to duration of symptoms:
Chronic urticaria: urticaria that has been continuously or intermittently present for >6 weeks.
Chronic urticaria is classified into 2 subtypes:
Chronic spontaneous urticaria: spontaneous appearance of wheals, angioedema, or both ≥6 weeks due to known or unknown causes.
Inducible urticaria, for example delayed pressure urticaria, heat urticaria, solar urticaria, symptomatic dermatographism, vibratory angioedema, aquagenic urticaria, cholinergic urticaria, and contact urticaria.
Some people have urticaria that is complicated by angioedema, a swelling of the deeper dermis and tissues (e.g., mucosal surfaces), with laryngeal edema potentially causing respiratory distress and death. Angioedema is commonly associated with urticaria and may occur at any age. It may not necessarily be seen at the first urticarial episode, and its risk increases with greater exposure to the allergenic substance. Symptoms are typically numbness, pain, or paresthesias. Angioedema without urticaria should prompt further evaluation.
- Acute spontaneous urticaria
- Chronic spontaneous urticaria
- Chronic inducible (physical) urticaria
- Drug eruptions
- Insect bite
- Viral exanthem
- Atopic dermatitis
- Allergic contact dermatitis
- Irritant contact dermatitis
- Erythema multiforme
- Stevens-Johnson syndrome
- Auriculotemporal syndrome
- Bullous pemphigoid
- Cutaneous mastocytosis
- Systemic mastocytosis
- Urticarial vasculitis
- Transfusion reactions
- Serum sickness
- Cold-induced urticaria, Muckle-Wells syndrome, neonatal multisystem inflammatory disease
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