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Peanut allergy in child
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arowland25 posted:
Hi! My son is 3 and just had testing done for food allergies. All skin testing came back negative for food allergies, but blood testing showed a class 3 peanut allergy. The blood work was done by his GI specialist b/c he has been having some tummy issues. So I called our allergist and told her the results and she seems to think it's nothing to be concerned about???

Isn't any class of allergy something to be concerned with?
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DUKE MEDICINE
Michael H Land, MD responded:
Dear Arowland25,

This is a very, very common question and I answer this probably about 2-3 times per day in my clinic. This is a perfect example of how difficult it is to make a diagnosis of food allergies and why food allergies are sometimes over-diagnosed in the medical community, particularly by non-allergy specialists (and even some allergy specialists).

What is important to realize is that the "Class" interpretation of the results for allergen specific IgE levels is something that is provided by the laboratory to aid in interpretation of the lab values. I never want to know what the "class" is but what the actual value is, personally, because each food is interpreted differently.

What the tests actually measure are the levels of a specific antibody (IgE) that your son's body has created to identify potential allergens (like peanut). The immune system may create antibodies to many different foods, environmental allergens, and even other substances (medicines or venom) and it may have no relevance. I often tell patients that Just because you have the antibody does not necessarily mean you have allergies.

A lot of my patients get really caught up in what the "test says" or what the "result showed" but they forget to consider what it is looking for and how it should be (very carefully) interpreted. These labs are all tools that help a physician confirm a suspicion based on a very clear history of symptoms.

If someone told me that they ate peanut butter every day, 5 days a week and enjoyed eating peanuts at baseball games, loved peanut butter in chocolate, etc., never had any immediate allergic reactions to it, and then one day had a blood test that showed a detectable peanut IgE (class 3, perhaps), then I would deem that to be not clinically relevant. That person is not peanut allergic. They should continue eating peanuts. That blood test never should have been done in the first place (by the way, this happens a lot!).

However, another person who ate peanuts for the first time and then immediately had lip swelling, hives, trouble breathing, and vomiting would be at a high suspicion for having peanut allergy. A blood test taken from this patient could have the exact same result as the person above, and I would tell this second person that they DO have a peanut allergy and they have to strictly avoid it and carry injectable Epinephrine.

Please note that this is a Completely different diagnosis for the same test result in two different patients.

What makes a diagnosis is not just the test result alone, but a combination of a strong history and confirmatory tests. A food challenge is sometimes necessary to make the diagnosis or also skin testing (for instance, if your son never eats peanuts so an actual reaction has never occurred because he has not ever wanted to eat them).

I would advise talking it over with your allergist and going over his diet carefully, specifically: does he eat peanut without any immediate reactions? If he has never had peanuts before, peanut allergy is a possibility, and this situation might need a food challenge to really make the diagnosis.

Here are a few news articles that talk about this problem:

New York Times


Wall Street Journal


I hope this helps! I have a personal interest in clarifying this confusing issue for patients since I see this sort of thing every day, and the last thing I want for anyone is to be told they are allergic to something that they are not.

Good Luck,
Michael
 
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arowland25 replied to Michael H Land, MD's response:
Thank you so much for clearing that up! That makes perfect sense!


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