A 34-year-old man visited our hospital with alopecia areata on the occipital scalp, which began to develop two months prior to his visit. He was sensitized with 0.2% diphenylcyclopropenone(DPCP) in acetone that was applied to the inner side of his right arm. Two weeks after sensitization, we applied DPCP on his bald lesion once weekly for skin challenge. Following the third application of DPCP, polycyclic erythematous target-like lesions developed around the sensitized area. A clinical diagnosis of erythema multiforme was made. Histologically, the target-like lesion showed few eosinophilic dyskeratosis, exocytosis, and hydropic de-generation of basal layer in the epidermis, and mononuclear infiltration around superficial blood vessels in the dermis.