Allergy Testing Overview
Allergy tests are a group of tests that are used to find out or confirm which substances are causing allergic reactions.
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
Description of the Test
There are several types of allergy tests:
- Blood testing—You will roll up your sleeve. The technician will clean the area with an antiseptic. An elastic band will be tied around the 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 technician will cover the site with a bandage. The 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 allergen (substance that causes the allergic reaction) will be applied directly to the skin. It may be applied with a shallow scratch or with a skin-prick needle. The needle will push the substance into the surface layer of the 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.
There are no special steps that you need to take after the test.
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.
Once specific allergens have been identified, you can take steps to avoid these triggers. This will help lessen allergic symptoms. Ask your doctor to give you strategies to control your allergies. Adjust your activities to avoid exposure to allergens that bother you.
American Academy of Allergy, Asthma, and Immunology
National Institute of Allergy and Infectious Diseases
Allergy Asthma Information Association
Calgary Allergy Network
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