Ultraviolet radiation and chemical requirements for experimental contact photosensitivity.

Contact photosensitivity to tetrachlorsalicylanilide was induced in albino guinea pigs. For the induction process, different types of ultraviolet radiation were employed and the effect of different doses of chemical was measured. Dose responses for ultraviolet radiation and chemical were determined for the production of positive photopatch tests in photosensitized animals. Successful contact photosensitivity was achieved when UVA alone was used for induction. Contrary to previously published reports, we found that UVB, chemical or physical irritation or immune potentiation were not required. In order to detect all photosensitized animals 0.1 ml of 1% TCSA and 1.65 J/cm2 of UVA were required to produce positive photopatch tests.