Diagnostic tests will help you and your child's health care provider or allergist know what substances cause your child's allergy symptoms. Knowing what substances cause the symptoms tells you what your child should stay away from. It also tells the provider what treatments might reduce symptoms. Diagnostic tests for allergy may include:
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Skin tests. These tests measure your child's level of IgE antibody response to certain allergens or triggers. They use small amounts of solutions that contain different allergens. The health care provider may give your child a shot (injection) of the solution under the skin. This is called an intradermal test. Or the provider may apply the allergens with a small scratch. A reaction would appear as a small red area after about 15 minutes. A reaction to the skin test does not always mean your child is allergic to the allergen that caused the reaction. This will be determined by your child's provider. Skin testing may be done on children who have had a severe life-threatening reaction to an allergen. Talk to your allergist if you are concerned about your child's previous reactions and skin testing. Children who have severe skin rashes (such as eczema) may not be able to be skin tested until their rashes are under control.
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Blood tests. These tests measure IgE antibodies to certain allergens in the blood. The blood test most often used is called RAST (radioallergosorbent test). Or a newer blood test called an ELISA ( enzyme-linked immunosorbent assay) may be done. Blood tests may be used when skin tests can't be done. As with skin testing, a positive blood test does not always mean your child is allergic to that allergen. It takes longer to get blood test results, and they may cost more than skin tests.
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Challenge test. This test is always supervised by an allergist. They give your child a very small amount of an allergen to breathe in (inhale) or eat. Then your child is closely watched for an allergic reaction. Don't try this at home.
Your child's provider will talk with you about the test results. They know your child's health history and will suggest the best options to manage or treat the allergy.
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