What is an Allergy Blood Test?
Allergies are a common and chronic condition that involves the body’s immune system. Normally, your immune system works to fight off viruses, bacteria, and other infectious agents. When you have an allergy, your immune system treats a harmless substance, like dust or pollen, as a threat. To fight this perceived threat, your immune system makes antibodies called immunoglobulin E (IgE).
Substances that cause an allergic reaction are called allergens. Besides dust and pollen, other common allergens include animal dander, foods, including nuts and shellfish, and certain medicines, such as penicillin. Allergy symptoms can range from sneezing and a stuffy nose to a life-threatening complication called anaphylactic shock. Allergy blood tests measure the amount of IgE antibodies in the blood. A small amount of IgE antibodies is normal. A larger amount of IgE may mean you have an allergy.
Other names: IgE allergy test, Quantitative IgE, Immunoglobulin E, Total IgE, Specific IgE
What is it used for?
Allergy blood tests are used to find out if you have an allergy. One type of test called a total IgE test measures the overall number of IgE antibodies in your blood. Another type of allergy blood test called a specific IgE test measures the level of IgE antibodies in response to individual allergens.
Why do I need an allergy blood test?
Your health care provider may order allergy testing if you have symptoms of an allergy. These include:
What happens during an allergy blood test?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for an allergy blood test.
Are there any risks to the test?
There is very little risk to having an allergy blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
If your total IgE levels are higher than normal, it likely means you have some kind of allergy. But it does not reveal what you are allergic to. A specific IgE test will help identify your particular allergy. If your results indicate an allergy, your health care provider may refer you to an allergy specialist or recommend a treatment plan.
Your treatment plan will depend on the type and severity of your allergy. People at risk for anaphylactic shock, a severe allergic reaction that can cause death, need to take extra care to avoid the allergy-causing substance. They may need to carry an emergency epinephrine treatment with them at all times.
Be sure to talk to your health care provider if you have questions about your test results and/or your allergy treatment plan.
Is there anything else I need to know about an allergy blood test?
An IgE skin test is another way to detect allergies, by measuring IgE levels and looking for a reaction directly on the skin. Your health care provider may order an IgE skin test instead of, or in addition to, an IgE allergy blood test.