For decades, scientists have been trying to figure out how to explain ballooning rates of food allergies and asthma. Peanut allergies, which now seem to plague elementary schools, have been particularly confounding.
The incidence of peanut and tree nut allergies in the United States quadrupled in the past 13 years, according to The New England Journal of Medicine. Young children in the United States are now allergic at what scientists believe are unprecedented levels—that's food allergies generally, and peanut allergies specifically. Peanut allergy is the country's leading food-allergy cause of anaphylaxis and death.
But what long seemed to be an inexplicable and growing threat now seems "extremely simple," said Scott Sicherer, a pediatrician and a researcher at the Jaffe Food Allergy Institute at Mount Sinai. "We might have caused this increase by telling people not to eat these things."
Sicherer was part of a team of doctors who helped shape a startling American Academy of Pediatrics recommendation in 2008 that said parents didn't have to wait to introduce foods like peanut butter to otherwise healthy babies. The new guideline represented a reversal from an earlier recommendation, established in 2000, that parents should wait until a child turned 3 years old to try foods associated with high risk of allergies. While doctors once believed that infant immune systems "weren't ready" for foods like nuts, eggs, and fish, Sicherer and other doctors began hypothesizing that avoiding such foods might prompt a more dramatic immune response later. "Maybe waiting longer and longer for the baby to eat that food, that was counterproductive, maybe their immune system was better off seeing it earlier," Sicherer told me. "We erased the previous recommendations because we looked at the literature and said, 'Wait a minute, there's nothing supporting it and maybe it's counterproductive.'"