photopatch testing

photopatch testing

(fō′tō-păch″) A test used to identify allergic reactions triggered by ultraviolet (UV) light (specifically, to UVA).

Patient care

Two equivalent samples of the putative allergen are prepared. Each is applied to one side of the upper back of the patient. One side is shielded from exposure to ultraviolet light, and the other is treated with UVA at standardized doses and intervals. The reactions of the skin on either side are compared.