This is used to evaluate a patient who presents with an allergic dermatitis. Patch tests used at Sand Lake Dermatology Center were developed by the North American Contact Dermatitis Society and include the most common allergens (triggers) that we see including fragrance, metals, and preservatives. The patches are applied on Friday and interpreted the following Monday and Wednesday. This is essential to determine the exact nature of an allergic skin rash so that avoidance of the trigger can be undertaken. Patch testing does not check for food allergies.