A case of allergic contact dermatitis to a shampoo containing zinc pyrithione associated with an eruption of pustular psoriasis is reported. The patient had had stable psoriasis for 5 years, and never any other skin disease. Within 1 week she developed severe generalized pustular psoriasis with many lesions where the shampoo was applied. Treatment with cyclosporin, 200 to 300 mg daily, cleared the eruption within 4 weeks, except for psoriasis of the scalp. Extensive patch testing revealed a relevant sensitization to zinc pyrithione. This case illustrates that a generalized pustular psoriasis can be provoked by a substance present in a hair shampoo. Short-term treatment with cyclosporin is valuable in exacerbations of psoriasis caused by allergic contact dermatitis.