ALLERGIC CONTACT AND PHOTOCONTACT DERMATITIS DUE TO PSORALENS IN PATIENTS WITH PSORIASIS TREATED WITH TOPICAL PUVA

The incidence and clinical features of allergic contact and/or photocontact dermatitis due to psoralens were examined in 371 patients with psoriasis treated with topical PUVA. The psoralen derivatives used in the study were 8-methoxypsoralen (8MOP), 3-carbethoxypsoralen (3CPs), 4,6,4'-trimethylangelicin (TMA) and 7-methyl pyridopsoralen (MPP). Of 371 patients treated with 8MOP, three (0.8%) developed an acute dermatitis in the PUVA-treated areas. This incidence was significantly lower (P < 0.01) than that for 3CPs (four of 10 patients) or that for TMA (six of 17 patients). None of the seven patients receiving MPP on PUVA had a reaction. It was confirmed that these dermatitis reactions were due to contact and/or photocontact allergy to psoralens by several methods that included patch and photopatch tests, photopatch test mapping, determination of the minimal erythema dose (MED) and immunohistochemistry.