People allergic to nuts 'may still be able to eat some types'

27 March 2017

People who are allergic to one tree nut may still be able to eat other types, researchers claim.

In a new study conducted by researchers at the American College of Allergy, Asthma and Immunology (ACAAI), it has been found that participants allergic to one nut, who have a positive blood or skin prick test to other tree nuts, may not be allergic to the other nuts.

The researchers 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 sensitivity to the additional tree nuts, more than 50 per cent of those tested had no reaction in an oral food challenge.

"Too often, people are told they're allergic to tree nuts based on a blood or skin prick test," said

allergist and lead author Dr. Christopher Couch. "They take the results at face value and stop eating all tree nuts when they might not actually be allergic."

Tree nuts include almonds, cashews, walnuts and hazelnuts, but not peanuts. It was further found that almost none of the people allergic to peanuts, but sensitised to tree nuts, were clinically allergic to tree nuts.

"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. "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."

An oral food challenge is deemed the most accurate way to diagnose food allergy, the researchers claim. 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 carried out under the care of a trained, board-certified allergist.

The full study has been published in journal Annals of Allergy, Asthma and Immunology.

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