Effects of PUVA on delayed hypersensitivity in the guinea-pig.

Guinea-pigs previously sensitized to dinitrochlorobenzene (DNCB) were topically treated with 8-methoxypsoralen solution and longwave ultraviolet light (PUVA). The animals showed moderate or no clinical and microscopic responses to an elicitation dose of DNCB given immediately after the period of treatment. Exposure to ultraviolet light or psoralen alone did not affect the allergic response. Ten days after PUVA treatment there was a normal eczematous reaction after application of DNCB.