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Are Nut Allergies Overdiagnosed?

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By    |   Monday, 27 Mar 2017 11:33 AM

People who have an allergy to a single type of nut are often told to avoid all nuts. But is that really necessary? A new study published in Annals of Allergy, Asthma and Immunology showed that more than 50 percent of people who have an allergy to one type of tree nut may not be allergic to other nuts.

People with a tree nut allergy are often advised to avoid other tree nuts based only on a positive blood or skin prick test. But you may not be allergic to the other nuts and the new study suggests you should consider having an oral food challenge to diagnose additional nut allergies, especially if you've never had a reaction to eating those tree nuts before.

"Too often, people are told they're allergic to tree nuts based on a blood or skin prick test," says allergist Dr. Christopher Couch, lead author of the study and member of the American College of Allergy, Asthma, and Immunology (ACAAI).

"They take the results at face value and stop eating all tree nuts when they might not actually be allergic," he said. "We examined records of 109 people with a known tree nut allergy to an individual nut. They were tested for other tree nuts they had never eaten before using blood or skin prick tests. Despite showing a sensitivity to the additional tree nuts, more than 50 percent of those tested had no reaction in an oral food challenge."

An oral food challenge is considered the most accurate way to diagnose food allergy. During an oral food challenge, the patient eats tiny amounts of the food in increasing doses over a period of time, followed by a few hours of observation to see if they have a reaction. An oral food challenge should only be conducted under the care of a trained, board-certified allergist. You should never do one on your own since if you are allergic, you could have a severe, life-threatening reaction.

"Previous studies suggested people with a tree nut allergy, as well as those with a peanut allergy, were at risk of being allergic to multiple tree nuts," said allergist Dr. Matthew Greenhawt, chair of the ACAAI Food Allergy Committee and study co-author.

"We found even a large-sized skin test or elevated blood allergy test is not enough by itself to accurately diagnose a tree nut allergy if the person has never eaten that nut. Tree nut allergy should only be diagnosed if there is both a positive test and a history of developing symptoms after eating that tree nut."

Dr. Greenhawt stressed the study did not include challenges to nuts the individual had a documented history of having a reaction to when eaten. "The practice of avoiding all peanut and tree nuts because of a single-nut allergy may not be necessary," says Dr. Greenhawt. "After an oral food challenge, people allergic to a single tree nut may be able to include other nuts in their diet."

For those who do have allergies, an Australian study found that probiotics may be helpful, although the study was conducted using children who were allergic to peanuts, not tree nuts. Researchers from Murdoch Childrens Research Institute gave children either a daily dose of a probiotic (Lactobacillus rhamnosus) together with a peanut protein, or a placebo. The amount of the probiotic remained the same throughout the trial, but the amount of peanut protein was gradually increased every two weeks.

After a maximum maintenance dose of  2 grams was reached, it was maintained until the end of the 18-month trial. Researchers found that an astonishing 80 percent of the children were able to tolerate peanuts compared to only 4 percent in the placebo group — a rate 20 times higher than the natural rate of resolution for peanut allergy.

According to the Journal of Allergy & Clinical Immunology, tree nut or peanut allergies affect approximately 3 million Americans.

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People who have an allergy to a single type of nut are often told to avoid all nuts. But is that really necessary? A new study published in Annals of Allergy, Asthma and Immunology showed that more than 50 percent of people who have an allergy to one type of tree nut may...
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2017-33-27
Monday, 27 Mar 2017 11:33 AM
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