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Am Fam Physician. 2002;66(4):626

What is allergy testing?

If you have a stuffy nose, trouble breathing (especially in the summer), or hives after eating certain foods, you may have an allergy. Allergy tests can help you and your doctor find out if these problems are caused by an allergy and which things you are allergic to. That way you can stay away from the things that trigger your allergic reaction.

What kinds of allergy tests are available?

There are skin and blood tests for allergies. Skin tests are used most of the time. There are three main kinds of skin tests. The first kind is called a “scratch” or a “prick” test. A tiny drop of testing fluid is placed on your skin. Then, the skin is pricked through the drop. After 15 minutes, the test site is checked for redness and swelling. There's a “prick” sensation when the testing is applied, but it doesn't hurt a lot. Usually, about 40 prick tests are needed for a full exam.

In the second kind of skin test, the testing fluid is injected into your skin (like a shot). This test is used to check for allergy to medicines (most often penicillin) and bee-sting allergy.

The third kind of skin test is called a patch test. A small patch of material soaked in testing fluid is taped on your skin. After 2 or 3 days, your doctor will take off the patch and look for redness and swelling in your skin. Patch tests are used to evaluate rashes caused by allergy to things that might rub against your skin.

Some commonly used medicines, like antihistamines, can interfere with skin tests. If you take these medicines, you have to stop taking them before skin tests can be done. Blood tests can be helpful if you need allergy testing, but you can't stop taking your medicines.

Why should I be tested for allergies?

It is not always necessary to have allergy tests. In some cases, it can be easier to skip the tests and go straight to taking allergy medicines. There are a number of safe and effective medicines that work well for most allergies. If these medicines do not work for you, or if you have severe allergy reactions, allergy testing may be helpful.

Allergy tests can help you find out what you are allergic to. Once you know what you are allergic to, you can try to stay away from it. The most common nose or lung allergies are to pollens, molds, dust mites, and cats. The most common food allergies are to peanuts, other nuts, wheat, milk, eggs, fish, and shellfish. Your doctor will also be able to tell what kind of allergy medicine is right for you. If your doctor finds out that your problems are not caused by an allergy, he or she can look for other causes.

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