A 38-year- old woman with burning-painful unilateral rash on one shin of 3 days duration. The patient suffered vitiligo on lower legs of many months duration. She had been treated with topical trisoralen solution plus sun light exposure at day time and combined mometasone furoate and tacrolimus in ointment base at night. One day after commecement of treatment she developed a localized but severe bullous rash confined strictly to the vitiliginous area on which the solution had been applied. This phototoxic (irritant contact) dermatitis reaction is commonly encountered in daily practice even sometimes with many folds dilution of trisoralen solution.