Cholinergic urticaria. A seasonal disease.

Nine young patients with cholinergic urticaria reported that the occurrence of the disease was restricted to winter. They were examined in a climatic room in winter and summer under three climatic conditions in each season (cold, comfort, and severe heat). All subjects experienced severe phenomena of cholinergic urticaria during the winter season when tested under comfortable climate and under severe heat load. No phenomena were elicited in the summer under any of the three climatic conditions or under cold climatic condition in the winter. This finding led to the assumption that symptoms appear in the sufferers only when exposed to heat or heat-producing exercise while unacclimatized to heat. Artificial heat acclimatization is winter resulted in disappearance of all clinical phenomena of cholinergic urticaria, lasting from a few days to two weeks.