Can giving young children peanuts actually prevent an allergy?

HOUSTON — Turning what was once conventional wisdom on its head, a new study suggests that many, if not most peanut allergies can be prevented by feeding young children food containing peanuts beginning in infancy, rather than avoiding such foods.

About 2 percent of American children are allergic to peanuts, a figure that has more than quadrupled since 1997 for reasons that are not entirely clear. There have also been big increases in other Western countries. For some people, even traces of peanuts can be life-threatening.

An editorial published Monday in The New England Journal of Medicine, along with the study, called the results “so compelling” and the rise of peanut allergies “so alarming” that guidelines for how to feed infants at risk of peanut allergies should be revised soon.

The study “clearly indicates that the early introduction of peanut dramatically decreases the risk of development of peanut allergy,” said the editorial, by Dr. Rebecca S. Gruchalla of the University of Texas Southwestern Medical Center and Dr. Hugh A. Sampson of the Icahn School of Medicine at Mount Sinai in New York City. It also “makes it clear that we can do something now to reverse the increasing prevalence of peanut allergy.”

In the study, conducted in London, infants 4 to 11 months old who were deemed at high risk of developing a peanut allergy were randomly assigned either to be regularly fed food that contained peanuts or to be denied such food. These feeding patterns continued until the children were 5 years old. Those who consumed the foods that had peanuts in them were far less likely to be allergic to peanuts when they turned 5.

Dr. Gideon Lack, a professor of pediatric allergy at King’s College London and the leader of the study, said the common practice of withholding peanuts from babies “could have been in part responsible for the rise in peanut allergies we have seen.”

Whether infants should be fed peanuts and other foods associated with allergies is one of the most common questions parents ask about introducing solid foods to their children, said Dr. Ruchi Gupta, associate professor of pediatrics at Northwestern University, who was not involved in the study. “And until now most of what we can say is there’s not very conclusive data.”

The American Academy of Pediatrics, in guidelines released in 2000, recommended that peanuts be withheld from children at risk of developing allergies until they were 3 years old.

In 2008, the academy revised its stance, saying there was no conclusive evidence that avoidance of certain foods beyond 4 to 6 months of age helped stave off allergies, but stopped short of recommending that parents give their young children such foods.

“There was no study showing that that was the right thing to do,” said Dr. Wesley Burks, chairman of pediatrics at the University of North Carolina, who was not involved in the new research. Now, with the new study, he said, there is such evidence.

The results of the study were presented on Monday at the annual meeting of the American Academy of Allergy, Asthma and Immunology in Houston.