Patch testing is performed in order to help determine if an allergy is causing an individual’s dermatitis. The process of patch testing usually takes 5-7 days and requires three appointments. Since some of the patch test chemicals and the marker used in the testing process may stain clothing, individuals should wear dark older clothing for the 5-7 days of patch testing.
This visit usually takes approximately 45 minutes. Substances that Dr. Guenther suspects might be causing the rash are applied to small disks which are then secured to the skin of the back or arms with hypo-allergenic tape. The patch tests are left on until your next appointment. To help ensure that the patches stay in place, limit back movement and do not do heavy exercise. Do not get the patch tests wet! You may take a bath if you are careful to keep your back dry. If you feel intense itching or burning under a particular patch, gently lift up the patch to see if there is any redness, swelling or blisters forming on the underlying skin. If the underlying skin looks normal, reapply the patch. If there is redness, swelling or blisters, you may remove that specific patch, but write down the number of the patch and call the office to let us know which patch test number is causing you problems. Antihistamines may be taken to decrease itching. If you notice any loosening just apply more tape to keep the originals in place.
Visit 2 (48 hours later):
The patch tests will be removed from your back at this visit. The areas where the chemicals were applied will be marked with a blue or black marker by the nurse or doctor. Please wear a dark colored or older shirt since the marker may sometimes transfer to your clothing. If the marker lightens, please have a friend or family member remark the circles. Remarking is usually required every 12 hours. You still must not get your back wet until the final patch test visit. Redness, swelling and blistering where a test substance was in contact with your skin indicate a positive patch test. It is sometimes difficult to assess true allergy from irritation. Dr. Guenther will determine whether a specific reaction indicates an allergy.
Visit 3 (48 hours later):
Not all patch test reactions are visible when the tapes are first removed. Some show up later. Most however show up within the 2-3 days after patch test removal. It is for this reason that there is a third visit. At the final visit, Dr. Guenther will look at your back for any reactions. It she determines that you have an allergy to one or more of the compounds, you will be given specific information regarding these substance(s) so that you can avoid exposure. After this visit, you may wash your back.