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 will be available immediately after testing is done.

Allergy skin tests

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. See a picture of a positive patch test reaction .

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 4 times the normal level.

Go to previous section	Go to top of page	Go to next section
Author:	Debby Golonka, MPH	Last Updated August 8, 2007
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Harold S. Nelson, MD - Allergy and Immunology
This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.