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    Allergy Tests and Asthma

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    Allergy Skin Tests continued...

    Intradermal tests can be more accurate, but sometimes they may be falsely positive. That means they show that you have an allergy when you actually don't. Intradermal tests are also more likely to cause an allergic reaction that affects your whole body.

    Patch test: Your doctor applies the allergen to a patch. You'll leave the patch on your skin on for 48 hours. If your skin turns red, gets irritated, and itches, the chances are great that you have an allergy.

    Allergy Blood Tests

    Your doctor may also recommend getting an allergy blood test.

    Radioallergosorbent test (RAST): This test may be less accurate than skin tests, but it's good for ultra-sensitive people who can't get a skin test because they might have a severe allergic reaction. It's also not affected by medications you may be taking. RAST is more expensive than skin tests. Doctors use this test for young children to rule out an allergy to something they breathe in.

    Quantitative immunoglobulin determination test: This measures levels of different immune system chemicals in your blood. It can help your doctor find out if your symptoms are caused by an allergy. This test isn't used often.

    WebMD Medical Reference

    Reviewed by William Blahd, MD on October 21, 2015
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