Allergy Blood Testing
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- Also Known As:
- Allergy Screen
- Formal Name:
- Allergen-specific IgE Antibody Test

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At a Glance
Why Get Tested?
To help diagnose allergies; sometimes to monitor the effectiveness of immunotherapy (desensitization) treatment
When To Get Tested?
When you have symptoms such as hives, dermatitis, nasal congestion, red itchy eyes, asthma, or abdominal pain that your health care practitioner suspects may be caused by an allergy
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.
Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.
The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.
If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.
Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”
For more information, please read the article Reference Ranges and What They Mean.
What is being tested?
Immunoglobulin E (IgE) is a class of antibody (immune protein) associated with allergic reactions. It is normally found in very small amounts in the blood. This test measures the amount of allergen-specific IgE in the blood in order to detect an allergy to a particular substance.
IgE is an antibody that functions as part of the body’s immune system, its defense against “intruders.” When someone with a predisposition to allergies is exposed to a potential allergen such as food, grass, or animal dander for the first time, that person becomes sensitized. The person’s body perceives the potential allergen as a foreign substance and produces a specific IgE antibody that binds to specialized mast cells in the skin, respiratory system, and gastrointestinal tract, as well as to basophils (a type of white blood cell) in the bloodstream. With the next exposure, these attached IgE antibodies recognize the allergen and cause the mast and basophil cells to release histamine and other chemicals, resulting in an allergic reaction that begins at the exposure site.
A total IgE test measures the overall number of IgE antibodies in the blood, while a specific IgE test measures for a response to individual allergens. Each allergen-specific IgE antibody test performed is separate and very specific; for example, it will test honeybee versus bumblebee, egg white versus egg yolk, and giant ragweed versus western ragweed. Groupings of these tests, such as food panels or regional weed, grass, and mold panels, can be done. Alternatively, the health care practitioner may pick and choose selectively from a long list of individual allergens suspected of causing a person’s allergies.
While the traditional method for blood testing was the RAST (radioallergosorbent test), it has been largely replaced with newer IgE-specific immunoassay methods. Some health care practitioners continue to refer to all IgE allergy blood tests as RAST even though it is not the exact assay that the testing laboratory uses.
Common Questions
View Sources
Sources Used in Current Review
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(July 2014) Blood Test: Allergen-Specific Immunoglobulin E (IgE). KidsHealth from Nemours. Available online at https://kidshealth.org/en/parents/test-ige.html. Accessed on 3/7/2018.
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(January 16, 2018) Allergy Skin Tests. Mayo Clinic. Available online at https://www.mayoclinic.org/tests-procedures/allergy-tests/about/pac-20392895. Accessed 3/7/2018.
Sources Used in Previous Reviews
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American Academy of Family Physicians (1999, January 15). Food Allergies: Just the Facts. American Family Physician [On-line serial]. Available online at http://www.aafp.org/afp/990115ap/990115f.html.
ARUP. Immunoglobulin E. Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_ijk4.htm.
Sicherer, S. (2001, April 5th last update). Food Allergy Testing: Questions and Answers. Food Allergy News Reprint [On-line information]. Available online at http://www.foodallergy.org/topics_archive/testing.html.
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Mayo Clinic Staff (2009 April 03). Allergy Skin Tests. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/allergy-tests/MY00131/METHOD=print. Accessed February 2010.
(© 2009). Tips to Remember: What is Allergy Testing? American Academy of Allergy Asthma and Immunology, [On-line information]. Available online at http://www.aaaai.org/patients/publicedmat/tips/whatisallergytesting.stm. Accessed February 2010.
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American Academy of Allergy Asthma & Immunology. (Updated 2013). Allergic Reactions: Tips to Remember. Available online at http://www.aaaai.org/conditions-and-treatments/library/at-a-glance/allergic-reactions.aspx. Accessed October 2013.
American Academy of Allergy Asthma & Immunology (@2010). Allergy Testing. Available online at http://www.acaai.org/allergist/allergies/treatment/diagnosing-allergies/pages/allergy-testing.aspx. Accessed October 2013.
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(July 18, 2012) National Institute of Allergy and Infectious Diseases. What Makes and Allergen an Allergen. Available online at http://www.niaid.nih.gov/topics/allergicDiseases/research/Pages/whatMakesAllergens.aspx. Accessed January 2014.
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