To help diagnose allergies; sometimes to monitor the effectiveness of immunotherapy (desensitization) treatment
Allergy Blood Testing
Allergy Blood Testing
Also Known As
Allergy Screen
Formal Name
Allergen-specific IgE Antibody Test
This article was last reviewed
on
This article waslast modified
on
April 25, 2018.
At a Glance
Why Get Tested?
When To Get Tested?
When you have symptoms such as hives, dermatitis, nasal congestion, red itchy eyes, asthma, or abdominal pain that your healthcare practitioner suspects may be caused by an allergy
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
Accordion Title
Common Questions
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How is it used?
The allergen-specific IgE antibody test is a blood test used to help diagnose an allergy to a specific substance or substances for a person who presents with acute or chronic allergy-like symptoms. This is especially true if symptoms are recurrent and appear to be tied to triggers, such as exposures to particular foods or environments, and if other family members are known to have allergies.
Other types of allergy tests may be performed by exposing a person to different substances under careful medical supervision (see Common Questions #1). The usefulness of these tests, however, can be affected by skin conditions, such as significant dermatitis or eczema, and by medications, such as histamines and some anti-depressants. With some tests there is also the potential for severe reactions, including one that may be life-threatening such as anaphylaxis. In these cases, the allergen-specific IgE antibody test may be ordered as an alternative, as it is performed on a blood sample and does not have an effect on the person being tested.
The allergen-specific IgE antibody test may also be performed to monitor immunotherapy (desensitization) or to see if a child has outgrown an allergy. It can only be used in a general way, however, as the level of IgE present does not correlate to the severity of an allergic reaction and someone who has outgrown an allergy may have a positive IgE for many years afterward.
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When is it ordered?
One or more allergen-specific IgE antibody tests are usually ordered when a person has signs or symptoms that suggest an allergy to one or more substances. Signs and symptoms may include:
- Hives
- Dermatitis
- Eczema
- Red itchy eyes
- Coughing, nasal congestion, sneezing
- Asthma
- Itching and tingling in the mouth
- Abdominal pain or vomiting and diarrhea
A test may also be ordered occasionally to help evaluate the effectiveness of immunotherapy or to determine whether a child has outgrown an allergy.
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What does the test result mean?
Results of allergy blood testing must be interpreted with care. Even if an IgE test is negative, there is still a small chance that a person does have an allergy. Similarly, if the specific IgE test is positive, a person may or may not ever have an actual physical allergic reaction when exposed to that substance.
Negative results indicate that a person probably does not have a "true allergy," an IgE-mediated response to the specific allergens tested.
An elevated allergen-specific IgE result indicates that the person tested likely has an allergy. However, the amount of specific IgE present does not necessarily predict the potential severity of a reaction. A person's clinical history and additional medically-supervised allergy tests may be necessary to confirm an allergy diagnosis.
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Is there anything else I should know?
Sometimes a health practitioner will look at other blood tests for an indirect indication of an ongoing allergic process, including a total IgE level or a complete blood count (CBC) and white blood cell differential (specifically eosinophils and basophils). Increases in these test results may suggest an allergy, but they may also be elevated for other reasons.
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What other tests are available for allergy testing?
Skin prick or scratch tests, patch tests, and oral food challenges are usually performed by an allergist or dermatologist. Your health care provider may also try eliminating foods from your diet and then reintroducing them to find out what you are allergic to. It is important that these tests be done under close medical supervision, as a life-threatening anaphylactic reaction is possible.
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My allergy test was negative, but I continue to have symptoms. What else could it be?
You could have an allergy-like condition that is not mediated by IgE for which there are no specific laboratory tests. You might have a genetic hypersensitivity problem, such as sensitivity to gluten with celiac disease or have an enzyme deficiency, such as a lactase deficiency causing lactose intolerance. Or it could be another disease that is causing allergy-like symptoms. It is important to investigate your individual situation with your healthcare provider's assistance. Test results alone cannot diagnose allergies. Results from any type of allergy test have to be interpreted along with your medical history by a healthcare practitioner who is trained to diagnose allergies specifically.
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My allergy symptoms are generally mild. How serious is this really?
Allergic reactions are very individual. They can be mild or severe, vary from exposure to exposure, get worse over time (or may not), involve the whole body, and can sometimes be fatal.
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Will my allergies ever go away?
Although children do outgrow some allergies, adults usually do not. Allergies that cause the worst reactions, such as anaphylaxis caused by peanuts, do not usually go away. Avoidance of the allergen and advance preparation for accidental exposure, in the form of medications such as antihistamines and portable epinephrine injections, is the safest course. Immunotherapy can help decrease symptoms for some unavoidable allergies but won't work for food and the treatment, which usually consists of years of regular injections, may need to be continued indefinitely.