The article presents information on drug photosensitization. Photosensitization of the skin by crude psoralen extracts from plants was recorded as early as 1400 B.C. Treatment of leukoderma with the psoralen-containing plant. Psoralea corylifolia appears in manuscripts from Eastern Turkistan, India, China and Egypt. Photosensitization of the skin may occur through pathways-phototoxicity and photoallergy. Phototoxic reactions are induced by photoactive drugs which absorb light energy and then contribute that energy to photo-chemical reactions which damage cellular DNA, cytoplasmic organelles or the cell membrane.