Anaphylaxis to 5-methoxypsoralen during photochemotherapy

Photochemotherapy is very effective for the treatment of skin diseases such as psoriasis, as well as for the prophylactic 'hardening' therapy of patie nts suffering from polymorphic, light eruption. The photosensitizers most w idely used for oral photochemotherapy are the furocoumarins 8-methoxypsoral en and 5-methoxypsoralen. Beside light-induced phototoxic reactions due to the photosensitizing activity of psoralens, side-effects after the oral int ake of psoralens are nausea and vomiting, headaches, anxiety and sleeplessn ess. We report a rare case of anaphylaxis. to 5-methoxypsoralen that develo ped during prophylactic 'hardening' therapy in a 36-year-old woman sufferin g from polymorphic light eruption. Anaphylaxis to 5-methoxypsoralen was est ablished by placebo-controlled oral provocation tests.