For scientists studying food allergies, peanuts have become a particularly elusive adversary.

There’s still no consensus on why the incidence of peanut allergies quadrupled in the United States in just over a decade. To complicate matters further, the advice on when babies should first try peanut-containing products has changed dramatically in that time.

Fifteen years ago, doctors told parents to wait until their babies were 3 years old before giving them peanut butter, eggs, and fish—the idea being that young immune systems couldn’t yet handle such foods. By 2008, the American Academy of Pediatrics had retracted those guidelines, suspecting that “we might have caused this increase [in allergies] by telling people not to eat these things," the pediatrician and food-allergy researcher Scott Sicherer told me last year.

Then came a landmark study: Last year, the New England Journal of Medicine published the results of long-awaited research finding that the introduction of peanuts to children in infancy “significantly decreased” a child’s likelihood of developing a peanut allergy. Kids who first tried peanuts as infants—in the first 11 months of life—ended up having an 81 percent lower rate of peanut allergy by the time they were 5 years old, compared with kids who avoided peanuts in that time.

Now there’s more evidence to suggest it’s good for babies to try peanuts in their first year of life. (Really, we’re talking peanut butter or other snacks containing peanut products; peanuts themselves are a choking hazard). The latest study, published this month in the New England Journal of Medicine, finds early exposure to peanuts may protect kids from developing peanut allergies—even if they later go a full year without eating them.

Researchers again focused on children at high risk of developing a peanut allergy, and found that babies who first tried peanuts as infants and continued eating them until they were 5 could go for a 12-month period of peanut avoidance without any increase in the prevalence of peanut allergy. There seemed to be other benefits among peanut-eaters, too: The kids who avoided peanuts until they were 5 years old were more likely to report having had other problems like eczema, lower respiratory tract infections, near-sightedness, and stomach bugs like gastroenteritis. “Together, these findings show that 4 years of consuming peanut was sufficient to induce stable unresponsiveness to peanut, independent of the level of subsequent consumption of peanut,” the study’s authors wrote.

Physicians in the United States are still working on developing new guidelines for peanut introduction, but the American Academy of Pediatrics interim guidelines say that doctors should recommend that children try peanut-containing products when they’re infants—ideally between 4 months old and 11 months old. Those guidelines specifically apply to kids at a higher risk of developing peanut allergies in the first place.

Of course, every baby is different, and every parent should ask their doctor about the appropriate time to introduce new foods. But the latest research supports the idea that early exposure to peanuts can be beneficial for children even as they get older.

“Overall, after the introduction of peanuts in the first year of life, peanut consumption for the following 4 years, and a year of abstinence from peanuts, the peanut-consumption group had a prevalence of peanut allergy that was 74 percent lower than the prevalence in the peanut-avoidance group,” the authors of the latest NEJM study wrote, “a finding that shows unresponsiveness to peanut after a long period of peanut avoidance.”