Allergen-Specific IgE Blood Test

Why this test may be ordered

• To help diagnose food allergies in people who have symptoms after eating certain foods.
• To help distinguish between a food allergy and a food intolerance or sensitivity.
• To see if allergies have gone away over time.

Preparation and collection

You may need to stop taking certain medicines and/or supplements before the test. Follow your provider's instructions.

A health care professional will insert a small needle into a vein in your arm to collect a small amount of blood into a test tube or vial.

There is very little risk. You may have slight pain or bruising at the needle site, but most symptoms go away quickly.

Understanding results

Your test results show the level of IgE antibodies specific to different foods. Higher levels may indicate a possible allergy, but this test alone cannot confirm a food allergy. Your allergist will interpret your results along with your symptoms and other tests.

• Higher-than-normal level of allergen-specific IgE antibodies: You may have a food allergy to that specific food. Limitation: A high IgE level does not confirm a food allergy. Some people with high IgE levels can eat the food without symptoms, and some with normal levels can have reactions. Next step: Your allergist will likely recommend further testing, such as a skin prick test or an oral food challenge, to confirm the allergy.
• Normal (or lower) level of allergen-specific IgE antibodies: You are less likely to have a food allergy to that specific food. Limitation: A normal IgE level does not completely rule out a food allergy. Rarely, people with normal IgE levels can still have allergic reactions. Next step: If your symptoms are strongly suggestive of a food allergy, your allergist may still consider other tests.

• This test cannot confirm a food allergy on its own.
• The level of IgE does not predict how severe an allergic reaction may be.
• False positives (high IgE without allergy) and false negatives (normal IgE despite allergy) can occur.

What to do next

If a food allergy is confirmed, you will need to avoid the trigger food. Your allergist will provide a management plan, including how to handle mild reactions and when to use an epinephrine autoinjector for severe reactions.

• What do my test results mean?
• Do I need additional tests?
• How should I prepare for an oral food challenge if needed?
• What foods should I avoid based on these results?
• Do I need to carry an epinephrine autoinjector?

Evidence source

U.S. National Library of Medicine: Allergen-Specific IgE Blood Test