Dermatology

Urticaria

Mast-cell mediator release causes short-lived, itchy, blanching weals; histaminergic angioedema and anaphylaxis can accompany urticaria, while isolated angioedema may instead be bradykinin-mediated and needs a different pathway.

Definition

Urticaria (hives) is a skin condition of transient, itchy weals due to dermal oedema, often with angioedema. It is classified as acute (less than 6 weeks) or chronic (6 weeks or more), and most chronic cases are spontaneous rather than allergic.

First principles

Urticaria is histamine released into the skin, nothing more mysterious

The central event in urticaria is activation of dermal mast cells and release of histamine and other mediators. Triggers may include infection, medicines, foods, physical stimuli or, in chronic spontaneous urticaria, an autoimmune process. The final common pathway produces superficial dermal oedema and itch, but a reported trigger does not prove an IgE-mediated allergy.

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