Background We previously demonstrated that the semipurified human sweat antigen causes skin reactions and histamine release from basophils via specific IgE in patients with atopic dermatitis (AD). Patients with cholinergic urticaria (ChU) also develop skin reactions and histamine release of basophils in response to autologous sweat.
Objectives To study whether or not patients with ChU share sensitivity for the sweat antigen with patients with AD and to study the clinical characteristics among patients with ChU and the relationship with histamine-release activity of basophils.
Methods The sweat antigen that induces histamine release from basophils of patients with AD was prepared by Con-A, anion-exchange and reverse-phase chromatography. Relationships between histamine-release activity against the sweat antigen and clinical features of patients with ChU were analysed.
Results Twenty-three of 35 patients with ChU showed > 5% net histamine release in response to the semipurified sweat antigen, whereas none of healthy controls did so. In patients with ChU, histamine release in response to semipurified sweat antigen significantly correlated with the level of serum IgE and eosinophil numbers in peripheral blood. Incidence of each atopic disease in patients with ChU tended to be higher than in the general Japanese population. When the patients were categorized according to their responses in the histamine release test, the positive group tended to show a higher incidence of AD and bronchial asthma compared with the negative group.
Conclusions ChU and AD may share hypersensitivity to common antigens in sweat. The sweat allergy and atopic diathesis are associated with each other.