(ŭr-tĭ-kā′rē-ă )
[Pronunciation]
[L. urtica, nettle]

An allergic reaction marked by multiple discrete swellings on the skin (wheals) that are intensely itchy and last up to 24 hr. The wheals appear primarily on the chest, back, extremities, face, or scalp.

SYN: hives

Figure: URTICARIA




See: allergy; angioedema

ETIOLOGY
Urticaria is caused by vasodilation and increased permeability of capillaries of the skin due to the release by mast cells of vasoactive mediators. The mast cell degranulation is due to an immunoglobulin E–mediated reaction to allergens (e.g., foods, drugs, or drug additives), heat, cold, and, rarely, infections or emotions. Urticaria is a primary sign of local and systemic anaphylactic reactions. It affects people of all ages but is most common between the ages 20 and 40. Angioedema is frequently associated with urticaria.

TREATMENT
Drugs that block histamine-1 (H₁) receptors (antihistamines) are the primary treatment for urticaria. The use of both H₁ and H₂ receptor blockers has been recommended but has not been proven more effective. Patients should avoid identified allergens. Corticosteroids are not usually used.

Subentries:
aquagenic urticaria
urticaria bullosa
cholinergic urticaria
chronic urticaria
cold urticaria
urticaria factitia
generalized heat urticaria
giant urticaria
urticaria haemorrhagica
urticaria maculosa
urticaria medicamentosa
papular urticaria
physical urticaria
urticaria pigmentosa
pressure urticaria
solar urticaria