Methotrexate and ultraviolet radiation.

Reactivation of a sunburn has been reported after the administration of methotrexate for cancer chemotherapy. A similar reaction is described in a patient with psoriasis who was receiving both coal tar with ultraviolet radiation for cutaneous lesions and methotrexate for arthritis. Knowledge of this poorly understood side effect of methotrexate is particularly important for physicians administering phototherapy and, perhaps, photochemotherapy.