What may come as a surprise to consumers doesn’t surprise allergists: Being allergic to one tree nut doesn’t mean you’re allergic to all.
A study published Monday, March 27, in the Annals of Allergy, Asthma and Immunology concluded that out of a sample of 109 people allergic to a specific tree nut, like Brazil nuts, walnuts, hazelnuts and cashews, more than 50 percent did not have an allergic reaction to other kinds of nuts. For individuals allergic to peanuts, which are legumes and not nuts, scientists learned almost none of them had tree nut allergies.
Researchers found that it is more accurate to be tested with an oral food challenge, which involves eating an increasingly larger amount of a particular food over a period of time, rather than a skin or blood prick test. Scientists used data from oral food challenges at the University of Michigan Division of Allergy and Clinical Immunology clinics from 2007 through 2015.
“The findings show that there is a wider margin of error than previously thought [with blood prick and skin tests],” lead author Dr. Christopher Couch told HealthDay. “A positive skin test and/or blood test to a nut does not always indicate a true allergy.”
Scientists discovered that although the participants allergic to specific nuts showed a sensitivity to the new tree nuts in blood prick and skin tests, over half didn’t have a reaction after going through the oral food challenge. Researchers “strongly suggest” individuals take the oral food challenge with an allergist’s supervision. Taking such a trial on your own is not advised.
“Skin tests and blood tests to foods are not absolute and we can see false positives,” Couch said. “An oral food test is the most objective test we have to determine if a patient is allergic or if they are tolerant to a particular food.”
More research is needed to conclude these findings, but Dr. Jonathan Spergel, who conducted a similar study last year, is not surprised.
“We have known this for a while,” the chief of the allergy section at Children’s Hospital of Philadelphia said. “What people with a nut allergy need to remember is that when they are buying nuts, be careful not to buy mixed nuts. That will only exacerbate their problem.”