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Knowing the foods that cause your child’s food allergy reactions can help you best manage their allergy, reduce stress, and avoid restricting their diet unnecessarily. To help diagnose a food allergy, an allergist may recommend allergy tests.

But allergy tests only tell part of the story. Instead, food allergy tests work with your child’s personal, medical, and symptom history to help your child’s doctor confirm their allergens.

What Do Food Allergy Tests Look For?

There are two categories of food allergies:

Food allergy tests are best for IgE-mediated food allergies. They are rarely recommended for non-IgE-mediated food allergies.

What Are the Most Commonly Used Food Allergy Tests?

There are four types of food allergy tests that are most often used by allergists:

  • Skin prick test
  • Specific IgE (sIgE) blood test
  • Component test
  • Oral food challenge

Skin Prick Test

Skin prick testing (SPT) is one of the most commonly used allergy tests. You may have heard it called a “scratch test.” With SPT, the allergist places a drop of an allergen on your child’s skin and the lightly pricks it. This causes the allergen to go into the top layer of the skin.

Skin prick test on a person's back

If your child has IgE antibodies – immune cells that react with an allergen and cause an allergic reaction – to the food, they will develop a red, itchy bump. This bump is called a wheal or a flare.

Just because your child reacts to the allergen doesn’t mean they are allergic to the allergen. But if your child has had symptoms in the past when eating the allergen, SPT can help confirm the allergy.

Specific IgE Blood Test

The specific IgE (sIgE) blood test measures levels of specific IgE in the blood for certain foods. This test was previously known as RAST or ImmunoCAP testing. The allergen will be introduced into a sample of your child’s blood to see if IgE antibodies are found.

Like SPT, a positive result doesn’t mean your child is allergic. It can be used to confirm a diagnosis if other factors suggest an allergy. Also, the results – or “class levels” – don’t relate to whether or not your child is more likely to have anaphylaxis. Your child can have a low class level and still have a severe allergic reaction.

Component Test

A component test is another type of blood test. It’s different from other tests because it looks at IgE levels in the blood to different proteins in a food instead of the whole food. These tests are designed to try and determine if your child’s IgE tests are elevated due to true food allergy or are false positives from cross-reactivity with inhalant allergens.

Oral Food Challenge (OFC)

The best way to know if your child is actually allergic to a food is to have them eat it during an oral food challenge (OFC) in an allergist’s office. It’s the gold standard for confirming whether or not your child has a food allergy.

A doctor observes a mother feeding her child during an oral food challenge to test for a food allergy

In an OFC, your child eats small, increasing amounts of their suspected food allergen. The allergist and their staff watch your child for a reaction and are prepared to treat any symptoms, if they arise. It’s the most reliable allergy test for food allergies.

What Should I Do If I Think My Child Has a Food Allergy?

If you think your child has a food allergy, see a board-certified allergist, if possible. They know how to look at your child’s full history along with allergy tests to confirm or rule out a food allergy. Avoiding foods without a proper diagnosis can lead to issues like food anxiety, poor quality of life, and poor nutrition – factors that can have a major impact on your child’s well-being, health, and development.

Medical review: June 2023 by David Stukus, MD

It is important to stay up to date on news about food allergies. By joining our community and following our blog, you will receive news about research and treatments. Our community also provides an opportunity to connect with other people who manage food allergies for support.

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  • Dr. David Stukus: KFA Medical Advisory Team Member
  • A doctor observes a mother feeding her child during an oral food challenge to test for a food allergy: A doctor observes a mother feeding her child during an oral food challenge to test for a food allergy
  • Skin prick test on a person's back: Skin prick test on a person's back

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Comments (46)

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I think it's important to differentiate between "food allergy" (IgE mediated) and "food sensitivity". Both are immune mediated reactions, but involve different mediators (chemicals). Both are reactions brought on by food and both can make you very sick, although it is the food allergy that is likely to be life threatening. Even the symptoms brought on by each can be similar. For example, abdominal pain, diarrhea,vomiting,headache,asthma,and eczema can be triggered by a food sensitivity as well as a food allergy.To make matters more confusing, an individual can have both food allergies, as well as food sensitivities. So, how does one tell the difference? While RAST and skin prick is used to detect food allergy, MRT (mediator release test) is used to detect food sensitivities. MRT is used by registered dietitians to create elimination diets tailored to individual needs. If RAST or skin prick tests are negative and it appears food is making you sick, then chances are you have a food sensitivity. OR, if you have avoided those foods to which you reacted positively on an allergy test and you still have symptoms, then you may also have a food sensitivity.

 

L

My daughter is now 13 and has always had belly issues.  She had skin and RAST testing done as a toddler with no indications of food allergies.  At 11 her belly isues worsened and RAST testing was redone with nujmerous positive results.  We did skin testing and she was found to be allergic to milk, egg yolk, and fish. She has what you term a Non-IgE mediated reaction.  Oncethe foods were fully eliminated from her diet her belly issues went away, she was no longer bloated and felt much better.  Based on teh article I am confused how to do a challenge on kids like my DD.  At this point we fully avoid all egg, but were hoping to try to add egg white after she is retested at her next annual visit.  But if both the skin and RAST  testing have high false rates what is the best way to do follow up testing?  Thanks in advance

N

Wow, that's great information thank you.  I'm just wondering what you suggest since we fall into the category of my son being tested for allergies at a young age due to his eczema; however, he never tried any of the food before. Now we have an Epi pen for him as he was diagnosed with anaphylactic allergies.  Thank you! 

M

Thank you for this very detailed explanation. However, I'm not sure I agree with this statement "if your child can eat a food without developing any symptoms, then they are unlikely to be allergic to that food." My son has tested negative to pretty much every allergy skin prick and blood test - only positive to hazelnuts one time and walnuts another time, both in skin prick tests. He suffered from severe eczema, head to toe, and we were looking for answers. There was no particular food that seemed to cause the eczema and he didn't suffer from any immediate allergic reactions - his eczema had developed slowly since birth. Since the allergy testing was inconclusive, we eliminated dairy, soy, gluten, some tree nuts, and corn for 30 days. His skin cleared up within days of starting the elimination diet. We added each of the foods back in slowly, each one over a four day period, and his reactions were obvious - instant itching, redness around the mouth, eczema within a few hours. With dairy he wheezes and has a mild asthma attack. Many of these are IgE mediated as you described above, I believe. So, the reason I disagree with your statement above is that it seems in some cases, if a child consumes a food they are allergic to (not anaphylactic) on a daily basis, it is possible allergy symptoms will not be obvious because the reaction is so gradual. If the food is removed completely for a given amount of time and cleared from the body, then you can see the body's true reaction to the food instantly.


I look forward to your comments.


Thank you.

Jennifer Roberge

JR
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