Blood Test: Immunoglobulin E (IgE)

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What It Is

An immunoglobulin E (IgE) test measures the blood level of IgE, one of the five subclasses of antibodies. Antibodies are proteins made by the immune system that attack antigens, such as bacteria, viruses, and allergens.

IgE antibodies are found in the lungs, skin, and mucous membranes. They are associated mainly with allergic reactions (when the immune system overreacts to environmental antigens such as pollen or pet dander) and parasitic infections.

Why It's Done

The IgE test is often performed as part of an initial screen for allergies. Symptoms of allergies may include hives, itchy eyes or nose, sneezing, nasal congestion, tight throat, and trouble breathing. Symptoms may be seasonal (as with allergies due to pollen or molds) or year-round (as with food allergies). They can range from mild to severe, depending on the child and the allergy.

IgE levels may also be elevated in children with parasitic infections.

Preparation

No special preparations are needed for this test. On the day of the test, it may help to have your child wear a short-sleeve shirt to allow easier access for the technician who will be drawing the blood.

The Procedure

A health professional will usually draw the blood from a vein. For an infant, the blood may be obtained by puncturing the heel with a small needle (lancet). If the blood is being drawn from a vein, the skin surface is cleaned with antiseptic, and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.

After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting blood for this test will only take a few minutes.

drawing_blood

heel_prick_illustration

What to Expect

Either method (heel or vein withdrawal) of collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a day or so.

Getting the Results

The blood sample will be processed by a machine, and the results are commonly available within a few days.

In some cases, the results of the IgE test will allow your doctor to make a diagnosis and prescribe treatment. More often, though, further testing (such as a skin test or allergen-specific IgE blood test) may be necessary to determine what particular allergen is causing the allergy.

Risks

The IgE test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn:

  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin causing a lump or bruise)
  • pain associated with multiple punctures to locate a vein

Helping Your Child

Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child can understand might help ease some of the fear.

Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax and stay still during the procedure, as tensing muscles and moving can make it harder and more painful to draw blood. It also may help if your child looks away when the needle is being inserted into the skin.

If You Have Questions

If you have questions about the IgE test, speak with your doctor.

Reviewed by: Steven Dowshen, MD
Date reviewed: February 2011



Related Resources

OrganizationAmerican Medical Association (AMA) The AMA has made a commitment to medicine by making doctors more accessible to their patients. Contact the AMA at: American Medical Association
515 N. State St.
Chicago, IL 60610
(312) 464-5000
OrganizationAmerican Academy of Allergy, Asthma, and Immunology The American Academy of Allergy, Asthma, and Immunology offers up-to-date information and a find-an-allergist search tool.
OrganizationAmerican Society of Hematology This group provides information relating to blood, blood-forming tissues, and blood diseases.
Web SiteThe Food Allergy and Anaphylaxis Network (FAAN) The FAAN mession is to raise public awareness, provide advocacy and education and to advance research on behavior for all of those affected by food allergies and anaphylaxis.


Related Articles

All About Allergies Up to 50 million Americans, including millions of kids, have an allergy. Find out how allergies are diagnosed and how to keep them under control.
Seasonal Allergies (Hay Fever) At various times of the year, pollen and mold spores trigger the cold-like symptoms associated with seasonal allergies. Most kids find relief through reduced exposure to allergens or with medications.
Blood Test: Allergen-Specific Immunoglobulin E (IgE) This test is done to check for allergies to specific allergens. It's especially useful in kids who've had life-threatening reactions to a certain allergen and for whom a skin-prick test would be too dangerous.
Blood Test: Immunoglobulin A (IgA) Checking IgA levels can help doctors diagnose problems with the immune system, intestines, and kidneys. It's also used to evaluate autoimmune conditions, such as rheumatoid arthritis, lupus, and celiac disease.
Blood Test: Immunoglobulins (IgA, IgG, IgM) Evaluated together, immunoglobulins (antibodies in the blood) can give doctors important information about immune system functioning, especially relating to infection or autoimmune disease.
Immune System The immune system, composed of special cells, proteins, tissues, and organs that protect against germs and microorganisms, is the body's defense against disease.
Allergy Shots Many kids battle allergies year-round, and some can't control their symptoms with medications. For them, allergy shots (or allergen immunotherapy) can be beneficial.




Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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