Allergy Patch Testing

patch testing Patch tests are the standard for diagnosing allergic contact dermatitis.

Please remember that patch tests have to be scheduled in advance after completing initial consultation with the doctor. In this test, two-three rectangular patches are applied on your back and left there for the next 48 hours. The patches are secured by additional application of hypoallergenic tapes. You return to the office in 48 hours for the first reading of the tests. The doctor reviews the test sites for any possible allergic or irritant reaction 30 minutes after removing the patches. Then you are sent home without the patches and are told to come back after another 24 hours for the second reading. At the time of second visit the doctor examines your back again for any possible reaction. It is very important to do the second reading because sometimes reactions may not show up at the time of first reading.

During the entire time for 72 hours it is very important that you minimize sweating. In addition, you should not take shower to avoid wetting the back. You can take sponge baths. Medications such as steroids [prednisone, prednisolone, Medrol Dosepak and steroid injections], topical steroid creams and chemotherapy for cancer can interfere with the patch test results and can cause false negative results. Please inform your physician if you have taken any of these medications in the preceding 4 weeks. Antihistamines such as Benadryl, Claritin, Zyrtec, Allegra, etc., do not interfere with patch testing and therefore can be continued.

Sometimes false positive reactions [the test is positive but you are not truly allergic to the test substance] occur if the patch test is done when the rash is severe. It is always better to wait until the rash gets better before doing the test.

Patch testing to antigens is an extremely safe procedure. Complications include flare-up of contact dermatitis. Rarely, severe reactions (allergic or irritant) can lead in some cases to blistering, necrosis, scarring, keloids, and light or dark pigmentation of the skin at the test site. Sometimes, persistent reactions or bacterial or viral infections may occur. An anaphylactic reaction may occur to antigens that are responsible for contact urticarial (hives like) responses. Sometimes patients are sensitized to an antigen by patch testing. Complications from patch tests with a standard series are rare. It is our policy to get informed verbal and written consent from you before applying patches.

If you experience significant itching, irritation or pain at the site, you should contact us immediately. You then remove the offending patch with the physician's permission and leave the other patches on.

The patch tests have 70% sensitivity and specificity. This means a negative test does not rule out allergic contact dermatitis. If you have a positive test, then you should find out if the test is true by strictly eliminating all products containing the offending chemicals and see if the rash resolves.

Most of the insurance companies cover the tests. Some insurance may require prior authorization. Please contact our office if you would like to schedule an appointment ((650) 556-9577).