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Zen_Again's avatar

Do you have allergies? Would you be interested to know that you might've been mis-diagnosed?

Asked by Zen_Again (9901points) May 14th, 2010

This article in the Times confirms what many, myself included, have thought over the years – that a lot of our so-called allergies are simply mis-diagnosed.

Do you have any allergies?

How do you treat them?

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10 Answers

Zen_Again's avatar

Some people can’t/won’t use links, so here’s the article:

Doubt Is Cast on Many Reports of Food Allergies
By GINA KOLATA
Many who think they have food allergies actually do not.

A new report, commissioned by the federal government, finds the field is rife with poorly done studies, misdiagnoses and tests that can give misleading results.

While there is no doubt that people can be allergic to certain foods, with reproducible responses ranging from a rash to a severe life-threatening reaction, the true incidence of food allergies is only about 8 percent for children and less than 5 percent for adults, said Dr. Marc Riedl, an author of the new paper and an allergist and immunologist at the University of California, Los Angeles.

Yet about 30 percent of the population believe they have food allergies. And, Dr. Riedl said, about half the patients coming to his clinic because they had been told they had a food allergy did not really have one.

Dr. Riedl does not dismiss the seriousness of some people’s responses to foods. But, he says, “That accounts for a small percentage of what people term ‘food allergies.’ ”

Even people who had food allergies as children may not have them as adults. People often shed allergies, though no one knows why. And sometimes people develop food allergies as adults, again for unknown reasons.

For their report, Dr. Riedl and his colleagues reviewed all the papers they could find on food allergies published between January 1988 and September 2009 — more than 12,000 articles. In the end, only 72 met their criteria, which included having sufficient data for analysis and using more rigorous tests for allergic responses.

“Everyone has a different definition” of a food allergy, said Dr. Jennifer J. Schneider Chafen of the Department of Veterans Affairs’ Palo Alto Health Care System in California and Stanford’s Center for Center for Primary Care and Outcomes Research, who was the lead author of the new report. People who receive a diagnosis after one of the two tests most often used — pricking the skin and injecting a tiny amount of the suspect food and looking in blood for IgE antibodies, the type associated with allergies — have less than a 50 percent chance of actually having a food allergy, the investigators found.

One way to see such a reaction is with what is called a food challenge, giving people a suspect food disguised so they do not know if they are eating it or a placebo food. If the disguised food causes a reaction, the person has an allergy.

But in practice, most doctors are reluctant to use food challenges, Dr. Riedl said. They believe the test to be time consuming, and worry about asking people to consume a food, like peanuts, that can elicit a frightening response.

The paper, to be published Wednesday in The Journal of the American Medical Association, is part of a large project organized by the National Institute of Allergy and Infectious Diseases to try to impose order on the chaos of food allergy testing. An expert panel will provide guidelines defining food allergies and giving criteria to diagnose and manage patients. They hope to have a final draft by the end of June.

“We were approached as in a sense the honest broker who could get parties together to look at this question,” said Dr. Matthew J. Fenton, who oversees the guidelines project for the allergy institute.

Authors of the new report — and experts on the guidelines panel — say even accepted dogma, like the idea that breast-fed babies have fewer allergies or that babies should not eat certain foods like eggs for the first year of life, have little evidence behind them.

Part of the confusion is over what is a food allergy and what is a food intolerance, Dr. Fenton said. Allergies involve the immune system, while intolerances generally do not. For example, a headache from sulfites in wine is not a food allergy. It is an intolerance. The same is true for lactose intolerance, caused by the lack of an enzyme needed to digest sugar in milk.

And other medical conditions can make people think they have food allergies, Dr. Fenton said. For example, people sometimes interpret acid reflux symptoms after eating a particular food as an allergy.

The chairman of the guidelines project, Dr. Joshua Boyce, an associate professor of medicine at Harvard and an allergist and pediatric pulmonologist, said one of the biggest misconceptions some doctors and patients have is that a positive test for IgE antibodies to a food means a person is allergic to that food. It is not necessarily so, he said.

During development, he said, the immune system tends to react to certain food proteins, producing IgE antibodies. But, Dr. Boyce said, “these antibodies can be transient and even inconsequential.”

“There are plenty of individuals with IgE antibodies to various foods who don’t react to those foods at all,” Dr. Boyce said.

The higher the levels of IgE antibodies to a particular food, the greater the likelihood the person will react in an allergic way. But even then, the antibodies do not necessarily portend a severe reaction, Dr. Boyce said. Antibodies to some foods, like peanuts, are much more likely to produce a reaction than ones to other foods, like wheat or corn or rice. No one understands why.

The guidelines panel hopes its report will lead to new research as well as clarify the definition and testing for food allergies.

But for now, Dr. Fenton said, doctors should not use either the skin-prick test or the antibody test as the sole reason for thinking their patients have a food allergy.

“By themselves they are not sufficient,” Dr. Fenton said.

loser's avatar

That’s very interesting. A friend of mine was recently shocked that she had some dairy and didn’t combust or something. I think I’m going to pass along your link. Unfortunately, I know I am allergic to shellfish. Anaphylactic shock is a pretty strong indicator.

aprilsimnel's avatar

Well, it’s too bad that this doesn’t help me. I’m allergic to cat dander. If I’m in an area for more than a couple of minutes where the little darlings are, I get hives, itchy, watery eyes, and I can’t breathe very well.

:(

meagan's avatar

I wish the title would have been more specific about food allergies on this fluther topic.

I doubt that allergy tests that are done on your back (patch tests, they’re called?) could be wrong. Thats the kind of testing I had done when I was really young. I’m suffer from cat allergies and a certain type of grass, but I’m also mildly lactose intolerant. I haven’t been medically diagnosed for the later, but some things you don’t need to visit a doctor for.

ParaParaYukiko's avatar

I used to be allergic to carrots as a child, actually. When I ate them, my tongue would start to burn. It wasn’t hugely unpleasant so I didn’t really think anything of it – I thought that happened to everyone. I was about 12 when I mentioned it to one of my parents and realized it was probably a food allergy. And then, literally a few weeks later, it went away. I can now eat carrots burn-free! So it’s definitely true what they say about growing out of allergies.

Anyway, as @meagan said, this article probably does not relate to any other allergies besides food-related ones. Patch tests (scratch tests maybe? I just had one last summer) seem to be pretty accurate, and the same way they can test for such allergies they can treat them. Too bad they can’t do that with food.

But now I wonder, how many kids really do have peanut allergies…? I miss my in-flight bag of peanuts on long plane rides.

Seek's avatar

Very true about growing out of food intolerances and allergies.

I was never tested for it, but I had a reaction to bananas. It sucks, because I love bananas, but even a couple of bites would give me the shakes. It was very unpleasant. Then, during my pregnancy I craved bananas for a while, and never had a reaction! And I haven’t had one since. However, for the first time in my life, I’m allergic to poison ivy. Not a fair trade, in my opinion, as I know what a banana looks like, but I have no idea how to recognize poison ivy, oak, and sumac. (never needed to!)

cazzie's avatar

@Seek_Kolinahr wow! that’s an amazing exchange. The potassium in bananas…. wow.. what a thing to first be allergic to an then need during your pregnancy. I needed Magnesium so I craved cinnamon.

Shellfish allergies are pretty much one or zero. I morn the loss of my consumption, but Graves disease is a hard task master and I need to do what I can.

I think that as we age, our hormones and endocrine system change and we don’t have the same histamine or antibody reactions that we used to have (especially if we’ve gone through the very difficult task of a pregnancy).

YARNLADY's avatar

That is all about food allergies – what about the rest of us who have air borne allergies – I’m so disappointed – your question mis-guided me.

noodlehead710's avatar

Allergies come in two types: IgE mediated allergies and IgM mediated allergies. IgE ones are figured out with blood tests using radioactive tags, or a skin test (the one with needles). IgM are in your gut so there isn’t really a good way to test for IgM food allergies.

@meagan is right to say that this article is basically about IgM allergies. This is why the article finishes by saying that the scratch/antibody tests aren’t sufficient. It’s possible to have IgE mediated alleriges but not IgM even to the same item. (Also vice versa). Thus a skin test might not show that you’re allergic to milk for example, but you may have a reaction when ingesting it. Also you could test positive for skin allergies but not have a problem with ingestion (depending of course on the severity of the IgE allergy).

There is a lot of controversy (this article preferred the term chaos) around food allergy testing, so it would be interesting to see what the report that the article referred to was all about. Certainly the misdiagnosing of simple intolerances and acid reflux as ‘allergies’ doesn’t help. Thanks for the interesting article!

Zen_Again's avatar

@noodlehead710 Thanks for the informative clarification. Welcome to fluther.

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