Allergy Blood Test
An allergy blood test measures the levels of immunoglobulin E (IgE) antibodies in your blood to help identify specific substances triggering an allergic reaction.
What is an Allergy Blood Test?
An allergy blood test measures immunoglobulin E (IgE), an antibody your immune system produces when it perceives a harmless substance—an allergen—as a threat. While small amounts of IgE are normal, elevated levels indicate an allergic response to triggers such as pollen, dust, mold, animal dander, certain foods (like peanuts or shellfish), or medications (like penicillin).
What is it used for?
There are two primary types of tests:
- Total IgE test: Measures the overall amount of IgE antibodies in the blood.
- Specific IgE test: Measures the amount of IgE produced in response to one specific allergen.
Why do I need an allergy blood test?
Providers order these tests if you exhibit symptoms such as sneezing, stuffy nose, itchy eyes, hives, digestive issues, or respiratory distress. Blood tests are often preferred over skin tests if you have severe skin conditions, are taking medications that interfere with skin testing, or are at risk for a severe allergic reaction. They are also frequently used for young children.
What happens during the test?
A health care professional will draw a small amount of blood from a vein in your arm using a needle. The process is quick, usually taking less than five minutes.
Preparation and Risks
No special preparation is required, though you should inform your provider of all medications you take, as some (like antihistamines) may need to be paused. Risks are minimal, limited to minor pain or bruising at the puncture site.
What do the results mean?
A high result indicates a potential allergy, though the test does not predict the severity of the reaction. Because false positives (indicating an allergy when none exists) and false negatives (failing to detect an actual allergy) can occur, your provider may use these results in conjunction with your medical history or recommend a skin test. If you are at risk for anaphylactic shock, your provider will discuss an emergency treatment plan, which may include carrying an epinephrine auto-injector.