Allergy Testing
Definition
An allergy test is a group of tests to see if your body reacts to certain substances. They can show what your body reacts to and how severe the reaction is.
Reasons for Test
Allergy tests will show what is causing the symptoms. This will guide treatment. The best step in allergy treatment is to avoid the item causing a problem. Medicine may help if the allergen cannot be avoided.
Possible Complications
Allergy tests can cause itchiness near the site. Some people may have a severe reaction to the allergens but this is rare. The medical team will give treatment for any severe reactions.
What to Expect
Prior to Test
You may be asked about your symptoms and when they happened. It may help to narrow down the list of allergens to test for.
You may need to stop some medicine before some tests. The doctor will let you know before testing.
Description of the Test
Tests may include 1 or more of the following:
- Blood testing—You will be asked to sit. An area inside your elbow will be cleaned. 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. Once 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 items.
- Skin testing—A small sample of an allergen will be placed just under the skin. It may be placed with a shallow scratch or with a skin-prick needle. There will be a separate scratch or skin prick for each allergen. Redness and swelling will appear if you are allergic. It takes about 15 to 20 minutes to show. An allergen that caused a reaction may then be placed deeper into the skin for a second test.
- Patch testing—A patch with an allergen is placed on the skin. The patch will be left in place for 48 hours. The skin will be examined after 48 to 96 hours to look for a reaction. A reaction will cause itchy skin at the site. Some may have a blister-like sore. This test may be used for allergies like gold or nickel.
After Test
An antihistamine may be advised after the test. It will ease itchiness at the test site.
How Long Will It Take?
- For blood testing: a few minutes
- For skin testing: 15 to 20 minutes
- For patch testing: 48 hours with the patch on, 48 to 96 hours for observation
Will It Hurt?
You may have some irritation at the test site. Needle pricks or scratches are mild.
Results
Skin and patch test results will be seen right away. Blood test results may take more time.
Talk to your doctor about your test results. A test may point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.
Call Your Doctor
Call your doctor if you have a severe rash after the test. Let your care team know if you have any questions or concerns.
RESOURCES:
American Academy of Allergy, Asthma & Immunology
http://www.aaaai.org
National Institute of Allergy and Infectious Diseases
https://www.niaid.nih.gov
CANADIAN RESOURCES:
Canadian Society of Allergy and Clinical Immunology
https://csaci.ca
Canadian Allergy, Asthma and Immunology Foundation
http://www.allergyfoundation.ca
REFERENCES:
Allergic rhinitis. EBSCO DynaMed website. Available at:https://www.dynamed.com/condition/allergic-rhinitis. Updated April 19, 2019. Accessed February 14, 2020.
Allergy testing: tips to remember. American Academy of Allergy, Asthma & Immunology website. Available at: http://www.aaaai.org/conditions-and-treatments/library/at-a-glance/allergy-testing. Accessed February 14, 2020.
Bernstein IL, Li JT, et al. Allergy diagnostic testing: an updated practice parameter. An Allergy Asthma Immunol. 2008;100(3 Suppl 3):S1-1S48. Available at: https://www.allergyparameters.org/published-practice-parameters/alphabetical-listing/testing-download.
Last reviewed September 2019 by EBSCO Medical Review Board Marcin Chwistek, MD Last Updated: 10/20/2020