What Is a Blood Test? A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them detect problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working. What Is an Immunoglobulin E Test? An immunoglobulin E (IgE) test measures the level of IgE, a type of antibody. Antibodies are made by the immune system to protect the body from bacteria, viruses, and allergens. IgE antibodies are normally found in small amounts in the blood, but higher amounts can be a sign that the body overreacts to allergens. This can lead to an allergic reaction. IgE levels can also be high when the body is fighting off an infection from a parasite or with some immune system conditions. Why Are IgE Tests Done? An IgE test may be done if a child has signs of a possible allergy, immune system problem, or infection with a parasite. How Should We Prepare for an IgE Test? Your child should be able to eat and drink normally unless also getting other tests that require fasting beforehand. Tell your doctor about any medicines your child takes because some drugs might affect the test results. Wearing a T-shirt or short-sleeved shirt for the test can make things easier for your child, and you also can bring along a toy or book as a distraction. How Is an IgE Test Done? Most blood tests take a small amount of blood from a vein. To do that, a health professional will: clean the skin put an elastic band (tourniquet) above the area to get the veins to swell with blood insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand) pull the blood sample into a vial or syringe take off the elastic band and remove the needle from the vein In babies, blood draws are sometimes done as a "heel stick collection." After cleaning the area, the health professional will prick your baby's heel with a tiny needle (or lancet) to collect a small sample of blood. Collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Can I Stay With My Child During an IgE Test? Parents usually can stay with their child during a blood test. Encourage your child to relax and stay still because tensing muscles can make it harder to draw blood. Your child might want to look away when the needle is inserted and the blood is collected. Help your child to relax by taking slow deep breaths or singing a favorite song. How Long Does an IgE Test Take? Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once. What Happens After an IgE Test? The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days. When Are IgE Test Results Ready? Blood samples are processed by a machine, and it may take a few days for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it. Are There Any Risks From IgE Tests? An IgE test is a safe procedure with minimal risks. Some kids might feel faint or lightheaded from the test. A few kids and teens have a strong fear of needles. If your child is anxious, talk with the doctor before the test about ways to make the procedure easier. A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care for your child if the discomfort gets worse or lasts longer. If you have questions about the IgE test, speak with your doctor or the health professional doing the blood draw. Back to Articles Related Articles Learning About Allergies During an allergic reaction, your body's immune system goes into overdrive. Find out more in this article for kids. Read More Getting a Blood Test (Video) A blood test might sound scary, but it usually takes less than a minute. Watch what happens in this video for kids. Read More 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 medicines. Read More Allergies Your eyes itch, your nose is running, you're sneezing, and you're covered in hives. The enemy known as allergies has struck again. Read More Blood Test (Video) These videos show what's involved in getting a blood test and what it's like to be the person taking the blood sample. Read More Blood Test: Immunoglobulins (IgA, IgG, IgM) Immunoglobulins (antibodies in the blood) can give doctors important information about the immune system, especially relating to infection or autoimmune disease. Read More 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. Read More How Do Doctors Test for Allergies? Find out what the experts have to say. Read More Immune System The immune system is made up of special cells, proteins, tissues, and organs that defend people against germs and microorganisms. Read More How Do Doctors Test for Food Allergies? Find out what the experts have to say. Read More All About Allergies Millions of Americans, including many kids, have an allergy. Find out how allergies are diagnosed and how to keep them under control. Read More 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 help. Read More Blood Test: Allergen-Specific Immunoglobulin E (IgE) This blood test can check for some kinds of allergies. Read More What Is Skin Testing for Allergies? A scratch or skin prick test is a common way doctors find out more about a person's allergies. Read More 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. Read More Allergy Testing Doctors use several different types of allergy tests, depending on what a person may be allergic to. Find out what to expect from allergy tests. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.