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Allergy Tests

Results

A skin or blood test can tell you what substance, or allergen, may trigger an allergic response.

Skin tests

Skin tests work by exposing a person to suspected allergens and seeing if a reaction occurs. The results of the skin tests are available immediately after testing is done.

Allergy skin tests 1

Normal (negative):

No raised red areas (called wheals) are created by the allergen.

Abnormal (positive):

A wheal created by the allergen is at least 1/8 inch (3 mm) larger than the reaction to the negative control. The larger the wheal, the more certain it is that the person is allergic to that specific allergen.

Blood tests

Allergy blood tests look for substances in the blood called antibodies. Results of allergy blood tests are usually available in about 7 days.

Allergy blood tests

Normal (negative):

The levels of immunoglobulin E (IgE), a type of antibody, are the same as in a person who does not have allergies.

Abnormal (positive):

The levels of immunoglobulin E (IgE) antibodies for a particular allergen or group of allergens are above the normal level.

What Affects the Test

Reasons you may not be able to have a skin test or why the results may not be helpful include:

1 | 2 | 3 | 4 | 5 | 6 | 7

WebMD Medical Reference from Healthwise

Last Updated: March 12, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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