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Reasons for Test
What to Expect
Prior to Test
- What time it happened
- Where it happened
- What you ate
- What you have come in contact with
Description of the Test
- Blood testing—You will be asked to sit. An area inside your elbow will be cleaned with an antiseptic wipe. A large band will be tied around your arm. The needle will then be inserted into a vein. A tube will collect the blood from the needle. The band on your arm will be removed. After all the blood is collected, the needle will be removed. Some gauze will be placed over the site to help stop bleeding. You may also be given a bandage to place over the site. The process takes about 5-10 minutes. 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.
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?
Call Your Doctor
American Academy of Allergy, Asthma, and Immunology http://www.aaaai.org
National Institute of Allergy and Infectious Diseases http://www.niaid.nih.gov
Allergy Asthma Information Association http://aaia.ca
Canadian Allergy, Asthma, and Immunology Foundation http://www.allergyfoundation.ca
Allergic rhinitis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated April 24, 2014. Accessed August 18, 2014.
Allergy testing: tips to remember. American Academy of Allergy, Asthma, and Immunology website. Available at: http://www.aaaai.org/conditions-and-treatments/library/at-a-glance/allergy-testing.aspx. Accessed August 18, 2014.
Bernstein IL, Li JT, et al. Allergy diagnostic testing: an updated practice parameter. An Allergy Asthma Immunol. 2008 Mar;100(3 Suppl 3):S1-148. Available at: http://www.aaaai.org/Aaaai/media/MediaLibrary/PDF%20Documents/Practice%20and%20Parameters/allergydiagnostictesting.pdf. Accessed August 18, 2014.
- Reviewer: Marcin Chwistek, MD
- Review Date: 08/2014
- Update Date: 08/18/2014