A patch test is a method used to determine if specific substance may be causing inflammation of the skin. This inflammation is often referred to as contact dermatitis and can be classified as either irritant or allergic in nature. Nickel contact dermatitis is quite common and often seen with earring or jewelry allergy in less expensive jewelry.
The process of patch testing is quite straightforward. The suspected irritant is applied to the skin and held in place with an adhesive patch. Another patch with nothing is also applied as a control. After 48 hours, the patch is removed and the skin observed. The patient then returns to the office the following day and a final reading is performed. If the skin under the suspect patch is red and swollen, the result is positive and the person is presumed allergic to that substance. Treatment involved avoidance of the offending substance.