Allergy Testing
Definition |
Body Parts Involved |
Reasons for Procedure |
Complications |
What to Expect |
Outcome |
Call Doctor If
Definition
Allergy tests are used to determine which substances trigger allergic reactions in an individual. Two types of tests can be used to confirm an allergy diagnosis:
Blood tests - a small sample of blood is taken and tested for dozens of different allergens. Also called RAST tests or in-vitro tests.
Skin tests - applying suspected allergens to the skin to see if they elicit an allergic reaction (raised or irritated skin). Also called scratch tests or skin-prick tests.
Parts of the Body Involved
Skin testing is usually done on the arm or upper back. For blood testing, blood is drawn from the arm.
Reasons for Procedure
Allergy tests are used to determine which substances trigger allergic reactions in an individual. Once allergic triggers are identified, a person can take the necessary steps to avoid or lessen contact with the offending substance and reduce the chances of an allergic reaction
Risk Factors for Complications during the Procedure
None
What to Expect
Prior to Procedure - Keep a diary of your allergy symptoms. When you experience symptoms, write down the time of day, where you are, what you ate, and what you have come in contact with that could trigger the allergic reaction. Make sure to bring the diary with you to your doctor's appointment.
During Procedure – A blood sample will be taken from a vein in your arm or suspected allergens will be applied to your skin.
Anesthesia – None
Description of the Procedure
Blood testing – A sample of blood will be drawn from your arm. To do this, you will roll up your sleeve and the nurse or lab technician will tie a tourniquet around your upper arm. A needle will be inserted into a vein in your arm near the inside of your elbow and a small amount of blood will be drawn into a vial. The blood sample will be sent to a laboratory where it will be tested to determine what substances you are allergic to.
Skin testing – The suspected allergen is applied directly to the skin, usually on the forearm or back. The substance is either applied to a shallow scratch made on the skin or a skin-prick needle pushes the substance into the surface layer of the skin. For every allergen tested, you will have a separate scratch or skin prick. If you are allergic to one of the test substances, redness and swelling will appear at the site usually within 15 to 20 minutes.
After Procedure – There are usually no special instructions or restrictions after allergy testing.
How Long Will It Take?
Blood testing - Drawing the blood takes approximately 3 minutes. Laboratory results time varies depending on the laboratory. Results are generally available within a few days or a week.
Skin testing - If you are allergic, a reaction will usually develop in about 15 to 20 minutes.
Will It Hurt? There may be mild irritation where the substance is applied to the skin.
Possible Complications – Allergy testing carries minimal risk.
Blood testing – A small bruise or collection of blood under the skin may develop at the site of the needle stick.
Skin testing – There may be some mild irritation at the test site.
Average Hospital Stay – None. This test is performed in your doctor's office or in a clinic or hospital laboratory.
Postoperative Care – None
Outcome
Once specific allergens have been identified, steps can be taken to avoid these triggers and lessen allergic symptoms. Ask your doctor to give you detailed information on ways to take control of your allergies. Tailor your activities to avoid exposure to allergens that bother you, such as tree and grass pollens, dust mites, molds, specific foods, latex, or environmental and household irritants. Once you are diagnosed, pay close attention to possible triggers and discuss these with your doctor.
Call Your Doctor If Any of the Following Occurs
- A severe rash develops where suspected allergens were applied to your skin
SOURCES:
American Academy of Allergy, Asthma, and Immunology
Journal of the American Medical Association—Asthma Information Center
Last reviewed May 2001 by Medical Review Board
