Allergic to any tree nut? Don't worry, now you can eat some

If you have a particular tree nut allergy, then generally you are being asked to avoid every kind of nuts.

But now, a new research suggests that you should consider having an oral food challenge to properly diagnose additional nut allergies, especially if you've never had a reaction to eating those almonds, chestnuts and pistachios before.

The study, published in journal of Annals of Allergy, Asthma and Immunology, showed that among people allergic to one nut who have a positive test to other tree nuts, more than half passed an oral food challenge to other tree nuts without a reaction.

Passing an oral food challenge means you are not allergic to that nut. Tree nuts include almonds, cashews, walnuts and hazelnuts, but not peanuts.

"Too often, people are told they're allergic to tree nuts based on a blood or skin prick test," said lead study author Christopher Couch.

"They take the results at face value and stop eating all tree nuts when they might not actually be allergic," he added.

The team examined records of 109 people with a known tree nut allergy.

They were tested for other tree nuts that they had never eaten before using blood or skin prick tests.

The results revealed, despite showing 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.

"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," said co-author Matthew Greenhawt.

"The practice of avoiding all peanut and tree nuts because of a single-nut allergy may not be necessary," said Greenhawt, adding, "After an oral food challenge, people allergic to a single tree nut may be able to include other nuts in their diet.