Single exposure to ultraviolet irradiation and elicitation of human allergic contact dermatitis.

Ultraviolet radiation has been stated to inhibit afferent as well as efferent phases of allergic contract dermatitis. In this controlled study 17 female patients with nickel allergy were studied by three different protocols after an initial determination of their degree of hypersensitivity. They were patch tested with nickel sulfate immediately after UVB, 4-6 days after UVB, or immediately after external PUVA. Neither depressing nor enhancing of the allergic reaction was observed when compared to non-irradiated controls. The role of Langerhans cells as antigen-presenting cell playing an important role in the elicitation phase of allergic contract dermatitis is discussed and questioned.