DermatologyPending review

Urticaria

Mast-cell degranulation releases histamine into the superficial dermis, causing local vasodilation and fluid leak that produce short-lived, itchy, blanching weals: the same mechanism that, in deeper tissue or on a larger scale, becomes angioedema or anaphylaxis.

In a nutshell

Mast cell degranulation releases histamine into the superficial dermis, causing the vasodilation, fluid leak and nerve stimulation that produce itchy, transient, blanching weals. The same process deeper in the tissue is angioedema, and systemically is anaphylaxis.

Classic presentation

Sudden-onset itchy, raised, blanching weals, each fading within 24 hours, sometimes with associated swelling of the lips or eyes.

Key points

Urticaria, angioedema and anaphylaxis are the same mast-cell mechanism at increasing tissue depth and systemic scale.

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Educational content pending clinical review. Not medical advice.