Information Media Zone: Skin Testing for Allergies

How Should I Prepare for an Allergy Skin Test?

Inform the health care provider who is going to perform your allergy skin test about all medicines you are taking, including over-the-counter drugs.

Since allergy medicines, including over-the-counter antihistamines, stop allergic reactions, you should not take them for a few days before the test. Talk to your doctor about discontinuing your allergy medicines prior to the test.

Your doctor will give you a list of medicines to avoid before the test, because there are other drugs that can interfere with the results. Since you may not be able to discontinue certain medicines, the doctor or nurse may perform a separate "control" test to determine if that particular drug will interfere with the scratch test.

How Long Does an Allergy Skin Test Take?

If you're having an allergy skin test, plan to spend about an hour for the entire appointment. For the scratch and intradermal skin tests, the allergen placement part of the test takes about 5 to 10 minutes. Then you will have to wait about 15 minutes to see how your skin reacts.

Patch tests take longer, as you must wear the patch for about 48 hours to determine if there is a delayed reaction. During this time, bathing and swimming should be avoided. You will return to the doctor after the specified period of time to have the area(s) checked.

Skin Testing for Allergies

Skin testing for allergies is used to identify the substances that are causing your allergy symptoms. It is often performed by applying an extract of an allergen to your skin, scratching or pricking the skin to allow exposure, and then evaluating the skin's reaction. It may also be done by injecting the allergen under the skin, or by applying it to a patch that is worn on the skin for a specified period of time.