Up to this point, researchers thought that allergies to tree nuts, which include cashews, almonds, walnuts, hazelnuts, macadamia nuts, pecans pistachios, and pine nuts, lasted a life time. It is estimated that 1%-2% of the United States population is allergic to peanuts, tree nuts or both. Previous research has shown that children allergic to peanuts have a 20% chance of outgrowing their allergy.

David M. Fleischer, MD, and colleagues from Johns Hopkins University School of Medicine, evaluated 278 children (Ages 3-21 years) to determine the percentage of those who will outgrow their allergy. Researchers also sought to determine what level of tree nut specific-IgE in the blood would be a safe level before testing the child through an oral food challenge, which is currently the best way to prove that a child has outgrown their food allergy.

The study found:
• Approximately 9% of children allergic to tree nuts outgrow their allergy, including children who have had a previous severe allergic reaction.
• Children who are allergic to multiple types of tree nuts are unlikely to outgrow their allergy.
• 58% of children with tree nut specific IgE levels of less than 5 kilounits per liter passed an oral challenge.

Based on these findings, researchers recommend that children with a current tree nut allergy be re-evaluated periodically by their allergist/immunologist to assess whether they have developed a tolerance and whether an oral challenge should be given.

While an ideal cut-off has not been established, researchers suggest that oral challenges should be considered in children four years and older, and who have less than five kilounits per liter of tree-nut specific IgE in their blood.

Since tree nut allergies were previously thought to last a lifetime, few patients underwent a re-evaluation to determine if their allergy still existed. They were simply told to avoid tree nuts, and were prescribed epinephrine to take in the event a severe reaction occurred. However, based on the results of the current study, it is now clear that periodic reevaluation is warranted. While only 9% will outgrow their allergy, researchers stress that it is important that these patients be identified so that they no longer need to worry about this otherwise potentially deadly allergy.