Immediate Wheal Reactivity to Autologous Sweat in Atopic Dermatitis Is Associated with Clinical Severity, Serum Total and Specific IgE and Sweat Tryptase Activity.

Background: Sweating can worsen atopic dermatitis (AD). The purpose of this work was to study the associations between reactivity to autologous sweat and the clinical severity of AD as well as investigate the possible wheal-inducing factors of sweat.

Methods: Intracutaneous skin tests with autologous sweat were performed on 50 AD patients and 24 control subjects. In skin biopsies, tryptase and PAR-2 were enzyme and immunohistochemically stained. The associations between skin test reactivity and sweat histamine concentration, tryptase or chymase activity levels, tryptase or PAR-2 expression and AD clinical severity or IgE levels were investigated.

Results: The wheal reactions in the intracutaneous tests with autologous sweat were positive, weakly positive and negative in 38, 34 and 28% of the AD patients, respectively, and in 4, 46 and 50% of the healthy controls, respectively (p = 0.008). In AD, the wheal reaction was associated significantly with clinical severity, serum total and specific IgE levels and sweat tryptase activity, but not with sweat histamine and chymase. In nonlesional AD skin, the percentage of PAR-2+ mast cells (MCs) or the number of tryptase+ MCs did not differ significantly between the intracutaneous test reactivity groups.

Conclusion: Reactivity to autologous sweat correlates with the clinical severity of AD, and tryptase may be one of the factors involved in the sweat-induced wheal.