Allergy Blood Test
Reviewed
An allergy blood test measures the amount of allergy-causing antibodies called immunoglobulin E (IgE) in the blood. It helps find out if you have an allergy. There are two general types: total IgE and specific IgE.
Preparation and collection
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.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Physical risks: minimal; slight pain or bruising at needle site; most symptoms go away quickly.
- False-positive: sometimes results may say you have an allergy when you do not; this may happen if your body has a slight reaction to substances in certain foods that you may have eaten before the test.
- False-negative: it is uncommon for a blood test to show you do not have an allergy when you actually do.
- Total IgE test does not show what you are allergic to or how serious your allergy may be.
- Specific IgE test amount does not predict how serious your allergy may be.
What to do next
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.