From Big Medical Encyclopedia

BLISTER (urtica) — one of primary elements of skin rashes; slightly towering, accurately delimited, bespolostny formation of various sizes and a form (oval, linear, ring-shaped), light pink, red or white color. Are observed at a small tortoiseshell, a disease of Dyuringa and nek-ry other dermatosis century, are followed by a severe itch or burning. Arise on any sites of skin century, is more rare on mucous membranes, extraordinary quickly, sometimes almost instantly; exist of several minutes till several o'clock and pass completely. V.'s education can be caused endogenous (most often on the mechanism of allergic reaction) and exogenous factors (a burn by a nettle, stings of insects).

At some persons B. develop on site mechanical irritation of skin (so-called dermo-or an autographism). In V.'s development functional vascular disorders in the form of increase in permeability of capillaries have crucial importance. Patogistologiya — a trichangiectasia and acute limited hypostasis, preferential papillary layer of a derma. In edematous liquid the histamine and biologically active agents possessing histamine-like action are found.

O. K. Shaposhnikov.