Researchers suggest tree nut allergies may be diagnosed too freely

Are tree nut allergies holding you back from enjoying some salty snacks? Well, a new study suggests that the common practice of telling patients allergic to one tree nut to avoid all other tree nuts may not be necessary.

The study, published by the American College of Allergy, Asthma and Immunology (ACAAI), found that many patients with tree nut allergies proved not to be allergic to other nuts.

Patients were given an oral food challenge using tree nuts different from the ones they had already been proven allergic to. An oral food challenge, according to the ACAAI, is considered the most accurate way to determine a food allergy. During this test, a person consumes a controlled amount of the food being tested over a period of time, while a doctor supervises any potential 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 Matthew Greenhawt, a co-author of the study. “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.”

The researchers found that more than 50% of 109 people with a specific tree nut allergy had no reaction during an oral food challenge with other tree nuts.

Greenhawt advises patients to verify suspected allergies in the simplest way: by trying food out under the observation of a medical professional. “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,” he said.

“The practice of avoiding all peanut and tree nuts because of a single nut allergy may not be necessary,” he added. “After an oral food challenge, people allergic to a single tree nut may be able to include other nuts in their diet.”

Allergies vs. sensitivities

Some of the individuals tested in the study have previously tested positive for a tree nut sensitivity using a blood or skin prick test. A sensitivity isn’t a true allergy, though.

What differentiates allergies from other food reactions is that during an allergic reaction, the immune system itself responds. Allergic reactions are also far more dangerous, and can be deadly, in the case of anaphylaxis.

During an allergic reaction, large amounts of an antibody found in the blood, called immunoglobulin E (IgE), are produced. Mast cells, which are specific cells in all body cells, are activated as well, especially in certain parts of the body, including the nose, throat, eyelids, lungs, skin and gastrointestinal tract. These mast cells mediate allergic reactions by releasing chemicals like histamine and heparin.

Neogen’s Food Safety Division offers allergen testing kits for a wide variety of targets, including tree nuts. For more information, click here.

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