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This article was published 19/9/2016 (1898 days ago), so information in it may no longer be current.
Patients’ lack of understanding about allergies and perceived food sensitivities has led them to avoid foods they don’t have to and could result in nutritional deficiencies, a new scientific review published in the Canadian Medical Association Journal says.
Winnipeg allergist Dr. Elissa Abrams and New York allergist Dr. Scott H. Sicherer of Icahn School of Medicine at Mount Sinai, Jaffe Food Institute, wrote their CMAJ article after examining recent Canadian, American and international guidelines — as well as 100 different scientific studies.
The article, published on Sept. 6, discourages Immunoglobulin G (IgG) testing offered by alternative practitioners such as naturopaths.
"Many guidelines, including Canadian guidelines, have said that this testing has no room in the diagnosis of food allergy or intolerance," says Abrams, an immunologist with the University of Manitoba who specializes in pediatric allergies.
"If you’re looking specifically for food allergy, I think that the best guidance — or the optimal guidance —would come from somebody trained in allergies."
IgG tests can cost hundreds of dollars. They aim to detect antibody responses to a wide range of foods. Most naturopathic practitioners who administer IgG tests classify antibody reactions as abnormal food sensitivities whereas allergists do not. Abrams says such tests lead to unnecessary avoidance of foods patients may not be allergic to.
"There is also a smaller risk that somebody who is IgE allergic, truly allergic, will have negative IgG testing and will reintroduce a food that they’re truly allergic to into their diet."
An estimated two to 10 per cent of people have food allergies. Most of these people are children, says the CMAJ article. Allergies in the U.S. have increased from 3.4 per cent to 5.1 per cent between 1997 and 2011, according to the review.
One prevalent theory is the so-called hygiene hypothesis, which suggests that overuse of antibiotics and antimicrobials may be responsible for wiping out beneficial bacteria in the stomach that protects from allergic reactions.
Self-reported rates of food allergy are much higher than their true prevalence, says the CMAJ article. It cites a population-based cohort study involving 3,623 children that found 35 per cent of parents perceived food reactions in their children — much different than the five per cent rate in the general population.
The standard first-line testing used by allergists looks for IgE (or immunoglobulin E) reactions. This testing can use the skin-prick method, in which a small drop of the allergen is placed on the skin that could produce an irritation within 15 minutes. It can also use a blood test that aims to measure an IgE reaction to foods.
Even though the CMAJ piece does not recommend the IgG test used by naturopaths, it points out that conventional allergy tests used by medical doctors also have shortcomings.
"The size of the (reaction) on your skin gives a likelihood that you truly are allergic, but doesn’t give any indication of how severe a reaction will be if you have a future reaction," says Abrams, noting that diagnostic testing is "highly sensitive" and often identifies "clinically irrelevant" sensitization.
Winnipeg dietitian Gina Sunderland is noticing an increasing number of clients with extensive lists of food allergies. Although she takes allergies very seriously because they can cause life-threatening reactions, she questions clients who say they are allergic to milk but tell her they eat milk products regularly.
"Perhaps they are sensitive to large amounts of the sugar in milk, but they probably aren’t allergic," says Sunderland, noting that incorrect perceptions about the existence of food allergies can lead to a diet restricted in vital nutrients.
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