Enhanced weal and flare response to histamine in chronic idiopathic urticaria.

Weal and flare histamine dose-responses were measured in 30 normal subjects and 15 patients with chronic idiopathic urticaria. The log dose-response curves were shifted to the left corresponding to an increase in histamine potency of 2.5 for weal and 3.1 for flare. An enhanced response to histamine may be important in chronic idiopathic urticaria and comparison of potency of antihistamines in different subjects may be unreliable where initial weal response is abnormal.