Allergy Patch Testing
Patch tests are the standard for diagnosing allergic contact dermatitis.
Please bear in mind that patch tests have to be scheduled in advance after completing initial consultation with the doctor. In this test, two rectangular patches are applied on your back typically, on Tuesday 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. Typically, on Thursday 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 48 hours, typically on Saturday for the second reading. At the time of second visit the doctor examines your back again for any possible reaction. The second reading can be done anywhere from 96 to 144 hours after the initial application of the patches. 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 96 hours it is very important that you stay in cool environments and avoid vigorous work or activities to minimize sweating. In addition, you should not take shower to avoid wetting the back. However 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 or Allegra 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 acute and is extensive. It is always prudent to wait until the rash gets better before doing the test.
Patch testing to antigens at standard concentrations and in standard vehicles is an extremely safe procedure. Complications include flare-up of contact dermatitis. Severe reactions (allergic or irritant) can lead in rare cases to blistering, necrosis, scarring, keloids, and light or dark pigmentation of the skin at the test site. Occasionally, persistent reactions or bacterial or viral infections may occur. An anaphylactic reaction may occur to antigens that are responsible for contact urticarial responses. Very rarely patients are sensitized to an antigen by patch testing. Complications from patch tests with a standard series are rare and are no excuse for the omission of this valuable test procedure. 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, remove the offending patch with the physician’s permission and leave the non-offending patch 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 the relevance of the test by strictly eliminating all skin and body care products and other products containing the offending chemicals and see if the rash resolves over time.
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.