Allergy Patch Testing

Allergy Patch Testing Is done to find what you might be allergic to.

Allergy Patch Testing is a procedure whereby you can be tested against a bank of cutaneous allergens to see “what you are allergic to?” This is particularly helpful for finding allergens that drive allergic dermatitis – such as PPD in hair dye, or Kathon in shampoo. It is not a perfect test and sometimes misses allergen and sometimes overcalls allergens. It is not useful for food intolerance, or airborne allergens.

Patch testing is an arduous test and is only undertaken after a full history has been taken, and generally, the history will give us some clues as to what to look for and what to test against.

Depending on the circumstances of the dermatitis and the suspected allergens found on history – different “sets” of patch testing can be used. For instance, there is a “cosmetic series” when looking at possible allergic dermatitis to a fragrance or preservative in a cosmetic product. There is a “hairdressers’ series” for looking at hand dermatitis in hairdressers – and so on.

Patch testing is an arduous test – and difficult to perform over summer, because you can’t shower, or sweat. You will not be able to wash their back, sweat, have a shower, etc for the full five days of the test, which is generally done Monday, Wednesday and Friday all in the one week.