Photosensitization of the Eye with Methoxsalen

Under ordinary circumstances long ultraviolet light (wavelengths longer than about 3,200 A.) is incapable of damaging the eye. Verhoeff and Bell 1 placed the upper limit of the keratitis spectrum in rabbits at 3,050 A., while Cogan and Kinsey 2 placed it between 3,060 A. and 3,260 A. The longer wavelengths are also incapable of causing certain reactions in the skin. The upper limit of the action spectrum for erythema in humans, for instance, is about 3,200 A. 3 Attention has recently been focused upon a photosensitizing agent, methoxsalen,* which alters the effect of sunlight upon the skin. 4,5 This substance is one of the active principles of the fruit of Ammi majus Linn, a plant which grows freely in the Nile Delta area. It has been used in Egypt for several centuries in the treatment of vitiligo and is currently being used in this country, among other things, for