Sensitization from a new hair dye allergen is reported: A 46-year-old shop cashier developed an exceptionally severe skin eruption on her scalp, face, upper chest and upper extremities. Her skin eruption relapsed 2 months later after her hair had been dyed, and she was referred to a dermatologist for patch testing. The True-test T M (Pharmacia) standard series was negative. We then obtained from the manufacturer 22 constituents of the hair dye, and further patch testing was performed. 2,7-dihydroxynaphthalene 0.1% aq. elicited a +++ reaction, whereas the other constituents were negative. A use test on the lower arm with the hair dye also provoked a reaction. 20 control persons were patch tested with 2,7-dihydroxynaphthalene 0.1% aq.: 19 were negative, but 1 without any history of hair dye dermatitis had a ++ reaction. In conclusion, most cases of allergic contact dermatitis from hair dyes have been caused by p-phenylenediamine and derivatives. Here we report sensitization from another chemical, namely 2,7-dihydroxynaphthalene, used as a coupler in permanent hair dyes.