Before the introduction of protective topical chemicals which absorb ultraviolet light, the only recourse for patients unable to tolerate even minimal exposure to sunlight was to stay indoors or wear opaque protective clothing. Two additional types of therapy, antimalarials and psoralens, have been developed in the last 15 years. None of these methods of protection is without disadvantages: Antimalarials are effective in some types of sunlight sensitivity, but ocular damage lessens their usefulness; psoralens induce pigmentation through "photosensitization"; and the effectiveness of the many topical agents varies greatly. Frequently the protective chemical is in a water-soluble vehicle and is easily removed by sweating, swimming, or rubbing. If not water-soluble, the vehicle may be greasy and difficult to remove or may soil the clothing.
A method which alters the natural "built in" optical filter of the stratum corneum was reported several years ago.1 The chemical reaction produced by a mixture