Methoxsalen belongs to the group of medicines called psoralens. It is used along with ultraviolet light (found in sunlight and some special lamps) in a treatment called PUVA to treat vitiligo, a disease in which skin color is lost, and psoriasis, a skin condition associated with red and scaly patches. Methoxsalen is also used with ultraviolet light in the treatment of white blood cells. This treatment is called photopheresis and is used to treat the skin problems associated with mycosis fungoides, which is a type of lymphoma.