PUVA or photochemotherapy is a type of ultraviolet radiation treatment (phototherapy) used for severe skin diseases. PUVA is a combination treatment which consists of Psoralens (P) and then exposing the skin to UVA (long wave ultraviolet radiation). It has been available in its present form since 1976. Psoralens are compounds found in many plants which make the skin temporarily sensitive to UVA. The ancient Egyptians were the first to use psoralens for the treatment of skin diseases thousands of years ago. Medicine psoralens include methoxsalen (8-methoxypsoralen), 5-methoxypsoralen and trisoralen.