Coprinus comatus (shaggy cap) is a potential source of aeroallergen that may provoke atopic dermatitis

Background: Basidiospores are universal components in the air and established as important causes of respiratory allergies. Recent reports indicate that aeroallergens may aggravate eczematous skin lesions in subjects with atopic dermatitis (AD), Objective: The aim of the study was to investigate whether spores of Coprinus comatus, a species of basidiomycetes, mag elicit delayed-type skin reactions in subjects with an atopic predilection, especially dermatitis. Methods: Sixty-six study subjects were categorized in groups having AD or respiratory allergy with regard to the skin prick test (SPT) reactivity to C comatus extract. Twenty nonatopic individuals served as control subjects. Atopy patch tests (APTs) were performed with extract of C comatus spore containing tissue at a concentration of 1.35 mg of protein per gram of petrolatum (Vaseline) and C comatus cap at a concentration of approximately 5 mg of protein per gram of petroleum jelly. APT reactions were evaluated after 48 and 72 hours. Results: Of the subjects with AD completing the study, 12 (32%) of 38 showed a positive APT reaction. with 8 (57%) also having a positive SPT response to C comatus. Only 1 (9%) of 11 subjects with asthma had a positive SPT and APT response to C comatus. No positive test reaction was observed in the nonatopic control subjects or in subjects with respiratory allergy and negative SPT responses to C comatus. Conclusion: Our results demonstrate that C comatus can induce delayed-type reactions in atopic individuals, particularly in those with AD. Because spores of Coprinus species are ubiquitous, basidiomycetes have to be considered as possible aeroallergens when investigating causes of eczematous skin lesions in AD.