ABSTRACT
Chronic urticaria is conventionally and arbitrarily defined as the daily or almost daily occurrence of wheals for 6 weeks or more (I). This encompasses a variety of different disorders that share whealing as the most prominent clinical feature (Table I). These include the physical urticarias. in which whealing occurs in response to a physical stimulus, usually applied directly to the skin. Cholinergic urticaria is usually included under the heading of a physical urticaria. although here the triggering stimulus is a rise in body temperature due to heat excercise or emotion. It also includes autoimmune urticaria. a relatively recently described entity (2-5) that will be considered in more detail below. Chronic urticaria. which cannot be ascribed to any of the above and for which an identifiable cause is elusive, is still a common and troublesome problem. termed chronic idiopathic urticaria. Of course co-existence of physical urticarias with chronic idiopathic urticaria or autoimmune urticaria frequently occurs in the same individual.
