Allergy Blood Test
An allergy blood test measures the amount of allergy-causing antibodies called immunoglobulin E (IgE).
An allergy blood test measures the amount of allergy-causing antibodies called immunoglobulin E (IgE). Antibodies are proteins that your immune system makes to fight foreign substances, such as viruses and bacteria . But your immune system may also make them in response to allergens. These are harmless substances, such as pollen and peanuts, that may cause an allergic reaction in some people. It's normal to have small amounts of IgE in your blood. But when you have an allergic reaction, your immune system sees the allergens as a threat and makes IgE antibodies. This increases the amount of IgE in your blood and causes your allergy symptoms. Common allergens include: Pollen Dust Mold Animal dander Certain foods , including nuts and shellfish Certain medicines , such as penicillin Allergy symptoms can be mild to severe, depending on the type of allergy you have. They can range from itching and sneezing to asthma or even a life-threatening condition called anaphylactic shock . Other names: IgE allergy test, Quantitative IgE, Immunoglobulin E, Total IgE, Specific IgE, RAST, CAP, ELISA, Allergy Screen
Why is this test ordered? Your health care provider may order allergy testing if you have symptoms of an allergy. These include: Stuffy or runny nose Sneezing Itchy, watery eyes Hives (itchy raised red patches on your skin) Diarrhea Vomiting Shortness of breath Coughing Wheezing Your provider may order an allergy blood test if you can't have allergy skin testing . Skin testing involves putting allergens directly on or into your skin. You may not be able to have skin testing if you: Have certain skin conditions Take certain medicines that may affect the results of the test Are likely to have a serious allergic reaction to the allergens used in skin testing In certain cases, providers may order allergy blood tests for young children because skin testing may be too uncomfortable for them.
Clinical Interpretation
A total IgE test result that is high means that you may have some kind of allergy. But the results of a total IgE test don't show what you're allergic to or how serious your allergy may be. A specific IgE test result that is high means that you may be allergic to the allergen that was tested. But the amount of IgE measured doesn't predict how serious your allergy may be. If the results from either type of test show that you could have an allergy, your provider may refer you to an allergy specialist or recommend a treatment plan. Your treatment plan will depend on what you are allergic to and how serious your symptoms are. If you're at risk for anaphylactic shock, you'll need to be very careful to avoid the things you are allergic to. You may need to carry an emergency epinephrine treatment (an epinephrine auto-injector) with you at all times. Anaphylactic shock is most common with allergies to certain foods, medicines, insect bites and stings , and latex . Ask your provider if you are at risk for anaphylactic shock and discuss any questions you have about your test results or your allergy treatment plan. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
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You don't need any special preparations for an allergy blood test. You may need to stop taking certain medicines before this test, such as antihistamines, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.