Nov. 9, 2005 -- Allergies to tree nuts such as cashews, almonds, walnuts, and pecans are sometimes outgrown, new research shows.
"Approximately 9% of patients outgrow tree-nut allergy, including some who had prior severe reactions," write doctors from Johns Hopkins University.
About one in five kids outgrows allergies to peanuts, add David Fleischer, MD, and colleagues. Peanuts are legumes, not tree nuts.
Nut allergies can prompt extreme and even fatal reactions. Any testing should be done by experts who are prepared to handle any allergic reactions.
Fleischer's study appears in The Journal of Allergy and Clinical Immunology.
The study included 278 patients from The Johns Hopkins Pediatric Allergy Clinic who had been diagnosed as being allergic to tree nuts.
Patients were from 3 to 21 years old. Cashews and walnuts were their most common tree-nut allergens, followed by pecans. A little more than two-thirds were also allergic to peanuts.
Most had a history of moderate-to-severe allergic reactions to tree nuts.
The patients' blood samples were checked for IgE, a chemical released by the immune system in response to allergies.
If IgE levels were low enough, patients were invited to get a tree-nut allergy test.
Participants ate cookies for the allergy test, not knowing if the cookies contained nuts.
A little culinary legwork was involved. Each type of nut was separately ground. Cinnamon and vanilla masked the nutty smell and taste. Molasses and oil made the cookies' color and fat content similar.
The cookies were served under the researchers' supervision. Emergency medicine was on hand, just in case.
A lot of eligible patients turned the test down. However, about 9% of their peers passed the test.
Who Outgrew Nut Allergies?
Most patients didn't outgrow their tree-nut allergies.
But nearly one in 10 did, some of whom had had a severe reaction in the past to tree nuts, the study shows.
Kids were more likely to have outgrown their tree-nut allergy if they were no longer allergic to peanuts.
That finding should be tested further, write the researchers. They note that parents of kids who had outgrown peanut allergies may have been more willing to let those kids take the nut-allergy test.
The odds of outgrowing tree-nut allergies weren't great for kids with allergies to more than one or two different tree nuts. Those children are "unlikely to eventually outgrow their allergy," write Fleischer and colleagues.
Retesting for Nut Allergies
Retesting may show some patients that they're no longer allergic to tree nuts. That can mean not having to be vigilant about avoiding nuts and treating accidental exposure, write the researchers.
However, they raise a few cautions:
- The potential exists for severe allergic reactions during testing.
- The ideal IgE levels for testing haven't been set.
- Follow-up testing shouldn't be done on kids who are less than 5 years old.
- Testing should only be done in proper settings with trained personnel.