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Allergies Health Center

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Skin Testing for Outdoor Allergies

Could you have an outdoor allergy to something like pollen or mold? You may need skin testing to be sure. Skin tests are a simple, easy way to show what's triggering your stuffy nose and cough.

Once you know what your allergic triggers are, you can protect yourself and control your symptoms.

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How Allergy Skin Tests Work

When you inhale a substance that you're allergic to, like ragweed, your body reacts. You’ll have symptoms like itchy eyes and runny nose.

Skin testing also triggers an allergic reaction, but only on the skin. The doctor will prick your skin with a tiny amount of an allergic trigger. It's safe and not very painful.

If you’re not allergic, nothing will happen. If you are, the area will swell and itch like a mosquito bite. That's how your doctor can tell what your triggers are.

Skin Test Types

There are two basic types of skin tests:

  • Standard skin test. The doctor places a tiny amount of the allergen on your skin, usually on your back or forearm, and then pricks or scratches the skin beneath.
  • Intradermal tests. The doctor will use a needle to inject the allergen a little deeper under the skin of your arm. You may need this test only if the others had unclear results.

Your doctor will probably test for many things at once. She will give you a physical exam and ask you questions, too. After the test and exam, your doctor should have a good sense of what triggers your allergies and what doesn't.

Skin tests are accurate, but they're not perfect. Doctors may need to figure out unclear results. It's important to work with a doctor who has a lot of experience with allergy testing.

Skin Testing Side Effects

If your body reacts to the allergen, you'll have swelling and some itchiness where the doctor injected it. These symptoms usually start within 15 minutes and fade away within 30 minutes.

Some people have a delayed reaction 24 to 48 hours later.

More serious allergic reactions are very rare. To be safe, doctors always do allergy testing in an office where they can watch you.

Skin Testing: Next Steps

After skin testing, your doctor can tailor your treatment and advise what you should do next. You may need:

  • More tests. If results weren't clear, your doctor may want more tests. Some people need challenge testing -- in which you would inhale or eat small amounts of the allergen -- or blood tests.
  • Environmental control at home. Once you know what you're allergic to, you can take steps to prevent exposure. If you're allergic to tree pollen, you can be careful to watch the calendar and keep windows shut when it's in the air.
  • Medication or allergy shots. In addition to reducing contact with your triggers, your doctor may prescribe medicine. Starting a series of allergy shots may reduce allergy symptoms.

WebMD Medical Reference

Reviewed by Laura J. Martin, MD on October 31, 2012

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