Diagnostic tests for nut allergy may be 'unreliable', say scientists

New Delhi: Scientists have deemed nut allergy tests inaccurate, saying that an allergy from one type of nut doesn't determine your sensitivity to all other nuts.

The scientists have further claimed 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 percent of those tested had no reaction in an oral food challenge," Couch said.

At present, the most accurate way to diagnose a possible food allergy is an oral food challenge, during which, 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.

(With PTI inputs)