[Differential diagnosis of urticaria].

Urticaria is usually a straightforward clinical diagnosis because of the distinctive appearance of both hives and angioedema. Because of differences in clinical manifestations, trigger factors, and duration, 12 different types of urticaria have been identified. The clinical appearance of urticaria may also differ over the course of time; an unquestionable case of urticaria may take on another appearance. Furthermore, there are associated diseases, which have to be taken into consideration for chronic urticaria.