Nut allergy tests may be inaccurate

Washington

Being allergic to one type of nut may not mean that you need to stop eating all other nuts, according to scientists who claim that certain diagnostic tests may be unreliable.

Researchers from American College of Allergy, Asthma and Immunology (ACAAI) in the US examined records of about 109 people with a known tree nut allergy to an individual nut.

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

Researchers found 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.

“Too often, people are told they’re allergic to tree nuts based on a blood or skin prick test,” said Christopher Couch of ACAAI.

“They take the results at face value and stop eating all tree nuts when they might not actually be allergic. Despite showing a sensitivity to the additional tree nuts, more than 50 per cent of those tested had no reaction in an oral food challenge,” Couch said.

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,” researchers said.

Tree nuts include almonds, cashews, walnuts and hazelnuts, but not peanuts. The study noted that nearly none of the people allergic to peanut, but sensitised to tree nut, were clinically allergic to tree nut.

The study was published in the journal Annals of Allergy, Asthma and Immunology.