Mechanisms of contact photosensitivity in mice. III. Predictive testing of chemicals with photoallergenic potential in mice.

The photoallergenic potential of various chemicals was assessed in mice. Mice were sensitized with applications of the test agent on the shaved abdomen; they underwent irradiation with black light on days 0 and 1. On day 5, ear lobes were painted with the chemicals and underwent irradiation with black light. The degree of the sensitivity was assessed by measuring the ear thickness 24 hours after challenge. Tetrachlorosalicylanilide, tribromsalan, bithionol, and chlorpromazine were photosensitizers. Hexachlorophene and sulfanilamide induced contact photosensitivity after pretreatment of mice with cyclophosphamide. Reactions of the recently discovered photosensitizers such as musk ambrette, 6-methylcoumarin, 7-methylcoumarin, and benzocaine were enhanced by cyclophosphamide pretreatment. Salicylanilide, salicylic acid, and 3,4-dichloroaniline failed to demonstrate photosensitization potential. This mouse model and cyclophosphamide pretreatment is a useful technique to determine photosensitization potentials for a variety of new chemicals.