The influence of ultraviolet radiation on allergic contact dermatitis in the guinea-pig. II. Psoralen/UVA radiation.

Guinea-pigs were sensitized by percutaneous application of dinitrochlorobenzene and exposed to UVA (320-400 nm) radiation following systemic administration of methoxsalen. This treatment diminished the response to an elicitation dose of the hapten administered 14 days later within the site of irradiation. The site of elicitation of the allergic response had to be included in the field of exposure, an reduction of the allergic response was observed only when the exposure to radiation was commenced at the time of induction of contact allergy. Established contact skin sensitivity was not affected by radiation.