Allergy Blood Test

What is an allergy blood test?

An allergy blood test is a type of allergy test that works by checking for antibodies called immunoglobulin E (IgE) in your blood. Antibodies are proteins your immune system produces in response to certain substances. If you have an allergy, your body usually produces more IgE in response to that allergen.

Common allergens include:

• Foods
• House dust
• Latex
• Insect bites and stings
• Molds
• Pet dander, urine and saliva
• Pollens
• Some medications (like penicillin)

Are there different types of allergy blood tests?

There are two types of allergy blood tests:

• Total IgE test: Measures the total amount of IgE antibodies in your blood. It doesn’t show what you’re allergic to and it’s not highly sensitive. Many people with subtle allergies may have a normal total IgE level.
• Specific IgE test: Measures the IgE antibodies in your blood in response to one particular allergen. It’s the more sensitive test of the two.

When is an allergy blood test needed?

You may need an allergy blood test if you have:

• Allergic rhinitis (hay fever), which is usually the result of environmental allergies like pollen, pet dander or molds
• Anaphylaxis, which is a severe and sometimes life-threatening allergic reaction to certain foods like peanuts, insect stings or other allergens

Your provider may also order an allergy blood test if you have allergy signs and/or symptoms like:

• Hives
• Itchy, red or watery eyes
• Shortness of breath (dyspnea)
• Skin rash
• Sneezing
• Sore throat (pharyngitis)
• Stuffy, itchy or runny nose
• Swollen lips, tongue, eyes or face
• Wheezing, tightness in your chest or allergic asthma

How does an allergy blood test work?

An allergy blood test detects higher-than-normal levels of IgE in your blood. When you have an allergy to a substance, your immune system makes IgE to fight off the allergen. As a result of this, your body makes substances such as histamine that, in turn, trigger the signs and symptoms of an allergy. The one thing an allergy blood test can’t usually show is how serious your allergy is.

How do I prepare for an allergy blood test?

You don’t need to do anything special to prepare for an allergy blood test.

What happens during an allergy blood test?

A blood draw for an allergy blood test only takes a few minutes. Here’s what you can expect:

1. A phlebotomist takes blood from a vein in your arm using a thin needle.
2. The needle might cause a mild pinch and some discomfort.
3. The phlebotomist fills a collection tube with blood and then removes the needle.
4. They place a small bandage on your arm.

What do allergy blood test results mean?

Everyone has some IgE in their blood, but elevated levels may indicate an allergy. Different labs use different brands of allergy blood tests, so the “scoring” system for results can vary from brand to brand. Allergy blood tests don’t usually show how serious your allergy is. That said, certain allergy tests (allergen components) can predict severity.

So, if you do have an allergy, talk to your healthcare provider about your risk for anaphylaxis. You may need to carry an emergency epinephrine injection with you at all times.

When will I know the results of my allergy blood test?

You may need to wait a few days for the results of your allergy blood test, though it could take more or less time. Ask your healthcare provider when you can expect your results.

Do allergy blood tests ever deliver false-positive results?

About 50% to 60% of all positive allergy blood tests results don’t result in having an allergy. This is why allergy blood tests should be ordered in the context of relevant signs and symptoms. Your provider may recommend additional testing if they’re concerned about your results.

When should I call my healthcare provider?

Contact your healthcare provider if you have questions about your allergy blood test results. Make sure you discuss what, if any, treatment is necessary to reduce your chances of having a severe allergic reaction.

Allergy blood test vs. allergy skin test: what’s the difference?

Allergy blood tests and allergy skin tests are two of the most common forms of allergy testing. During an allergy skin test, your healthcare provider creates tiny pinpricks in your skin and then applies an allergen to check for a reaction.

Skin tests deliver almost immediate results, but blood tests take a few days. Skin tests tend to be more accurate, but some people can’t have allergy skin tests. They won’t deliver reliable results if you have certain skin conditions, take antihistamines or have dark skin. In these cases, you may need an allergy blood test.