urticaria

an allergic reaction in an individual exposed to a substance to which he or she is hypersensitive, in which the response is manifested on the skin. Raised red patches develop, which may last for hours or days. There is intense itching. The sensitivity may be to certain foods, e.g. shellfish, and the effect may occur anywhere on the body but commonly erupts on the face and trunk. If it also affects the tongue or throat, there is danger of a blockage of the airway, which needs urgent attention.