To the Editor.—
A hereditary form of polymorphous light eruption affects Indians from the central plains of Canada and the United States1 to Central and South America.2 Exposure to sunlight leads to pruritic macular, papular, and vesicular eruptions, sometimes with pyoderma and scarring. Symptoms appear in early spring in those in the northern hemisphere and persist until late fall. Patients are sensitive to long exposure to ultraviolet radiation (symptoms appear after exposure through window glass) and therefore receive no protection from commercial sunscreens.The clinical aspects and seasonal appearance of symptoms are reminiscent of erythropoietic protoporphyria (EPP), but neither we nor Birt and Davis1 have detected elevated porphyrin levels in patients. Oral beta carotene is recommended for photoprotection of persons with EPP (Solatene package insert, Roche Laboratories, 1975). We reasoned that, since the disorder affecting American Indians resembles EPP, oral beta carotene may also protect these persons.