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Blister

Also known as: Urtica

A blister (Latin urtica) is a primary cell-free element resulting from acute limited edema of the papillary layer of the dermis. The element rises above the skin, has a flat surface, varies in shape and color from porcelain white to pink.

The main feature of a blister is that it is ephemeral (short-lived).

Etiology and pathophysiology

The blister is the main element of urticaria. Pathogenesis is associated with increased permeability of the vascular wall under the action of histamine and other mediators released by mast cells.

Clinical significance

The blister lasts from a few minutes to a few hours and disappears without a trace. It is accompanied by a pronounced, intense itching (“burning” as from nettles). The appearance of multiple draining blisters may be a sign of a systemic allergic reaction requiring emergency treatment.