Psoralen photoallergy caused by plant contact

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Abstract
A case of acquired photocontact allergy to furocumarins in plants is reported. Photopatch testing was performed with four psoralens [8‐melhoxypsoralen (8‐MOP), 5‐methoxypsoralens (5‐MOP), trimethylpsoralen (TMP) and imperatorin (IMP)]. The use of serial dilutions of the test compounds made it possible to differentiate between photoallergic and phototoxic reactions. 8‐MOP gave a positive eczematous text reaction down to a concentration of 0.0001% The reactions to 5‐MOP and IMP also were positive, while that to TMP was negative. Histopathological examination of a biopsy specimen from a positive test site showed changes consistent with photoallergic contact dermatitis.The multiple reactions could be explained on the basis of multiple sensitization, but cross reactions cannot be ruled out.