Nine percent of children allergic to almonds, pecans, cashews and other tree nuts outgrow their allergy over time, including those who've had a severe reaction such as anaphylaxis shock, according to researchers at the Johns Hopkins Children's Center.
Their study, reported in the November issue of the Journal of Allergy and Clinical Immunology, also found that clinicians can use blood levels of tree nut antibody (TN-IgE) as an accurate guideline in estimating the likelihood that a child has outgrown the allergy.
"What's crystal clear is that children with these allergies should be regularly re-evaluated," researchers concluded.
"Allergic reactions to tree nuts as well as peanuts (which are not nuts but legumes) can be quite severe, and they are generally thought to be lifelong," says senior author Robert Wood, M.D., director of the Division of Allergy and Immunology at the Children's Center. "Our research shows that for some children, however, lifelong avoidance of these nuts, found in countless food products, may not be necessary."
In the United States, an estimated one to two percent of the population is allergic to tree nuts (almonds, pecans, walnuts, cashews, Brazil nuts, hazelnuts, pine nuts, pistachios and macadamia nuts), peanuts or both. Wood and colleagues previously reported that as many as 20 percent of children outgrow peanut allergy and recommended that allergists periodically retest their patients. The current study explored whether the same held true for tree nuts.
Wood and colleagues evaluated 278 children, ages 3 to 21 years old, with a known allergy to tree nuts. Nine percent passed oral food challenges, the standard test to prove a child has outgrown a food allergy. Fifty-eight percent of children with TN-IgE levels of 5 kilounits per liter or less also passed the challenge.
"These findings give allergists a safe guideline in deciding whether to advise their patients to continue avoiding tree nuts, or whether it's time to try an oral food challenge to see if they've outgrown the allergy," says Wood. He cautioned that oral food challenges should be presented only under the close supervision of an allergist.
The study also found that, of children allergic to both peanuts and tree nuts, those who had outgrown their peanut allergy were more likely to outgrow the tree nut allergy. Children who are allergic to more than one type of tree nut are unlikely to outgrow their allergy.
The study was funded in part by the National Institute of Allergy and Infectious Disease.