Patch test is done to document aEUR'

Delayed type of hypersensitivity Patch test Patch test is done to detect contact dermatitis. Patch test detects type IV hypersensitivity (delayed) reaction to exogenous allergens. Patch test is a very simple technique which consists of applying the suspected agent or its chemical ingredients in specified concentration on normal looking skin on the back of the patient under separate patches for 48 hours and looking if this application produces dermatitis on the area,