• Allergy Testing

    Definition

    Allergies are an overreaction of your immune system to a specific item (allergen). Allergic reactions can range from mildly annoying like sneezing and itching to potentially life-threatening problems.

    Reasons for Test

    Allergy tests are a group of tests. They are used to identify the allergens that are causing your allergic reactions. Your doctor can use this information to help you make an allergy management plan.

    What to Expect

    Prior to Test

    Keep a diary of your allergy symptoms. When you have symptoms, write them down, including:
    • What time it happened
    • Where it happened
    • What you ate
    • What you have come in contact with
    For certain tests, your doctor may ask you to stop certain medications before the test.

    Description of the Test

    There are several types of allergy tests:
    • Blood testing—You will roll up your sleeve. The area will be cleaned with an antiseptic. An elastic band will be tied around your upper arm. A needle will be inserted into the vein. Blood will be collected into a vial. The elastic band will be untied and the needle will be removed. The blood sample will be sent to the lab for testing. The blood will be tested to see if it reacts to certain substances.
    • Skin testing—The suspected cause of your allergic reaction will be applied directly to your skin. It may be applied with a shallow scratch or with a skin-prick needle. The needle will push the substance into the upper layer of your skin. For every allergen tested, you will have a separate scratch or skin prick. Redness and swelling will appear if you are allergic. It usually takes about 15-20 minutes to appear. This may be followed by intradermal testing. In this case, the allergen is placed deeper into the skin.
    • Patch testing—Patches containing suspected allergens are placed on the skin. The patches will be left in place for 48 hours. You will be asked not to shower or get them wet. They will then be removed. The skin will be examined after 48-96 hours. If there is a reaction, the skin will become itchy at the site. A blister-like lesion may form.

    After Test

    Your doctor may recommend an antihistamine after the test. This can reduce itchiness at the test site. For severe allergies, make sure you have your epipen available.

    How Long Will It Take?

    • For blood testing: a few minutes
    • For skin testing: 15-20 minutes
    • For patch testing: 48 hours with the patch on, 48-96 hours for observation

    Will It Hurt?

    You may have mild irritation where the substance is applied to the skin. The needle pricks are small but can be irritating.

    Results

    Skin and patch test results are available immediately. Blood test results may take more time.
    Avoiding your specific allergens will help lessen your symptoms. You and your doctor can also discuss additional steps to help control your allergic reactions.

    Call Your Doctor

    After the test, call your doctor if you develop a severe rash or have any questions or concerns.

    RESOURCES

    American Academy of Allergy, Asthma, and Immunology http://www.aaaai.org/

    National Institute of Allergy and Infectious Diseases http://www.niaid.nih.gov/

    CANADIAN RESOURCES

    Allergy Asthma Information Association http://aaia.ca/

    Calgary Allergy Network http://www.calgaryallergy.ca/

    References

    Adkinson N, Yunginger J, Busse W, et al, eds. Middleton’s Allergy: Principles and Practice . 6th ed. Philadelphia, PA: Mosby; 2003.

    Allergy diagnostic testing: an updated practice parameter. American College of Allergy, Asthma & Immunology website. Available at: http://www.acaai.org/NR/rdonlyres/0B3BD12B-E34D-471B-994D-50DFD8E56A06/0/Dx%5FTesting%5F2008.pdf . Accessed July 21, 2009.

    Allergic rhinitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated July 2009. Accessed July 21, 2009.

    Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics . 17th ed. Saunders: Philadelphia, PA; 2004.

    Tips to remember: allergy testing. American Academy of Allergy, Asthma, and Immunology website. Available at: http://www.aaaai.org/patients/publicedmat/tips/whatisallergytesting.stm . Accessed December 7, 2012.

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