Patch testing is a test done to help diagnose airborne or skin allergies. This test is done by the dermatologist or allergist and is usually done in the office. This test helps determine if you are allergic to a number of different allergens at one time. It's called a patch test because a patch that contains a number of different allergens is placed on the back of the person being tested. The patch is put in place for a set amount of time, at which time the dermatologist or allergist will see what allergens you may be allergic to. Read on for what you can expect with an allergy patch test.

How Long Does the Test Take?

The patch test can take a few days to determine what you are allergic to. It can help to determine allergic reactions that may take a little longer to detect, as the reaction may be delayed.

What Type of Reaction Could Occur?

Usually with these types of allergens that are being tested, the patch test will result in red itchy bumps or welts on the skin. In more severe cases you could have a more widespread reaction on the skin, or in very severe cases, you could have itchy or watery eyes, or possibly even difficulty breathing.

What Information Do You Need?

You should have a medical history with you of any family history of allergies. You should also report any issues you have had in the past with allergies as well as what symptoms you may have had to help diagnose you better. Also have a list of medications you typically take, or bring them in so your physician can see what medications they are and how much of each you take daily, as some medications may end up causing issues with the results of your allergy test.

Can the Patch Get Wet?

The patch test should not get wet during the test, so you should avoid swimming or even bathing/showering while taking the test. If the patch gets wet, it could wash away the allergens and give you a false diagnosis. 

If think you may be allergic to airborne allergens, or you think you may have a skin allergy, a patch test may be ordered to determine the exact allergen causing you to have a reaction. Talk to your allergist or dermatologist about other things you can expect during a patch skin test.