A patch test is used to find allergic causes of eczema/dermatitis and some other types of skin reactions such as reactions to drugs, chemicals, metals, or foods.
Every patient is tested to the common chemicals known to cause allergy (such as nickel in metals, fragrances & other cosmetic ingredients, rubber chemicals found in gloves etc) together with additional allergens related to your specific problem e.g. work chemicals or extra ingredients of cosmetics or treatments. Each chemical is applied to a disc (about 1cm in diameter and then taped to your back in strips of 10). Each patient may be tested for allergy to up to 100 different substances. You will also be asked to take a small sample of any material that you think is causing a reaction (such as a cosmetic) to be tested as well.
This procedure consist of 3 office visits:
During the initial visit, test panel(s) will be placed on the back of you/your child. These panels consist of chemicals placed on shallow aluminum disks, which are taped to the skin. These panels must remain intact for 48 hours. This requires that they do not get wet or shift their location on the back. The selection of chemicals for testing will be determined by your allergist.
48 hours after patch placement, the patient will return to the clinic for patch removal and evaluation by a nurse.
72 hours after patch placement, the patient meets with the physician for evaluation and interpretation of patch testing results.
Your doctor may refer you for a patch test:
1. If you suspect an allergy as a cause of your eczema such as to cosmetic ingredients or hair dye
2. If you have eczema that is proving difficult to treat to ensure you are not allergic to ingredients of the treatment for your eczema
3. If you have a work related eczema/dermatitis