Responsiveness to autologous sweat and serum in cholinergic urticaria classifies its clinical subtypes

Background: It has been reported that patients with cholinergic urticaria have a type I allergy to autologous sweat; however, the pathogenesis of that disorder has not been fully elucidated. Objective: We investigated the responsiveness to autologous sweat and serum in patients with cholinergic urticaria in relation to their clinical characteristics. We further classified the clinical subtypes that are clearly characterized by responsiveness to in vivo and in vitro tests as well as their clinical features. Methods: Intradermal tests with autologous sweat and serum were performed in 18 patients with cholinergic urticaria. Histamine release from peripheral blood basophils induced by autologous sweat was measured. Results: Eleven of 17 patients with cholinergic urticaria showed positive reactions in skin tests with their own diluted sweat. Substantial amounts of sweat-induced histamine release from autologous basophils were observed in 10 of 17 patients. Eight of 15 patients with cholinergic urticaria showed positive reactions in the autologous serum skin tests. All 6 patients who developed satellite wheals after the acetylcholine test showed hypersensitivity to sweat. Further, patients whose eruptions were coincident with hair follicles showed positive responses to the skin test with autologous serum, whereas patients whose eruptions were not coincident with hair follicles did not. Conclusion: On the basis of these findings, we propose that cholinergic urticaria should be classified into 2 distinct subtypes. The first (nonfollicular) subtype shows strong positive reactions to autologous sweat and negative reactions to autologous serum. The second (follicular) subtype shows weak reactions to autologous sweat and positive reactions to autologous serum.