Immune reactions to Pityrosporum ovale in adult patients with atopic and seborrheic dermatitis.

Pityrosporum ovale is a lipophilic yeast commonly present in the seborrheic areas of the skin of adults. Fifty-five young adult patients with atopic dermatitis, 19 patients with seborrheic dermatitis, and 19 healthy control subjects were examined for immune reactions to P. ovale, including tests for specific IgE antibodies (prick test, histamine release), IgG antibodies and epicutaneous testing. IgE antibodies against P. ovale were found in two thirds of the patients with atopic dermatitis and were more frequent in patients with lesions predominantly in the seborrheic areas. In addition, some atopic patients had positive reactions to epicutaneous tests, which suggest that delayed allergic reactions to P. ovale may also be important. In patients with seborrheic dermatitis, no evidence of immediate or delayed hypersensitivity to P. ovale was found. IgG antibody levels were low in all groups.