Early peanut exposure can reduce likelihood of allergy

HOUSTON — Infants getting small but regular doses of peanut butter in their diet are less likely to develop an allergy to peanuts than similar babies who avoid peanuts altogether, a new study shows. The finding — in infants at higher-than-usual risk of peanut allergy — swings the balance of evidence in favor of early consumption and away from avoidance as a way to avert this troublesome food allergy.

The data call into question the notion that peanuts should be broadly avoided in infancy. In recent years, studies have hinted that early peanut consumption might be a better strategy to reduce the susceptibility to allergy.

“This is the first real data to support that emerging theory,” says Robert Wood, director of pediatric allergy and immunology at Johns Hopkins University in Baltimore. “The results of this study are dramatic. It’s not a borderline effect.”

Pediatric allergist Gideon Lack of King’s College London presented the findings February 23 at the American Academy of Allergy, Asthma & Immunology annual meeting. His team enrolled babies age 4 to 11 months who were deemed at elevated risk of peanut allergy because they either had severe eczema or were allergic to eggs. Each baby underwent a skin-prick test with a trace of peanut, which revealed any excess immune reaction. Allergic or highly reactive children were kept out of the study. The remaining infants were randomly assigned to get small doses of peanut butter in their diet at least three times a week or to avoid it altogether.

Among 530 babies who had no reaction to the peanut skin test at the outset, the peanut allergy rate at age 5 was 13.7 percent in the avoidance group and 1.9 percent in the peanut butter group. Among 98 other babies who had a slight or modest reaction to the skin-prick test, 35.3 percent of those assigned to avoidance were allergic by age 5. Only 10.6 percent of the 5-year-olds eating peanut butter were allergic. The report also appears online February 23 in the New England Journal of Medicine.

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In 2000, the American Academy of Pediatrics released guidelines calling on parents to avoid giving peanuts to babies who show any risk of allergy. But in 2008 those guidelines were rescinded because no clear evidence supported the policy unless an infant was clearly allergic. Since then, the issue has been up in the air for many babies, with some studies suggesting that peanut consumption might often be a better approach, says Wood. “The time is really right for this to lead to changes in recommendations, which were evolving without data,” he says.

Despite years of peanut avoidance by many families, peanut allergy rates in Western countries have risen in the last 10 years, reaching up to 3 percent. The key may lie in infants’ diets, says study coauthor George Du Toit, also a pediatric allergist at King’s College. While exclusive breast-feeding is recommended for the first six months, “less than 10 percent of countries achieve that. Young children are taking on complementary foods, weaning early,” he says. “We now need to embed peanuts within that.”

In 2008, Lack and Du Toit found that peanut allergy rates in Jewish children in the United Kingdom were 10 times as great as in Israel. The researchers noted that U.K. kids started consuming peanuts later than Israeli kids (SN: 12/6/08, p. 8). That suggested that time of peanut introduction mattered and led to the new study.

“This is a big step forward,” says immunologist Dale Umetsu of Genentech, a pharmaceutical company based in South San Francisco, Calif. The next challenge will be for pediatricians to interpret these findings. “In the field of medicine, we’re moving toward a one-size-doesn’t-fit-all way of thinking,” he says. Regarding peanuts, “some might benefit from early introduction and others may not.” He calls for skin-prick tests.

Writing in the New England Journal of Medicine, Hugh Sampson of the Icahn School of Medicine at Mount Sinai in New York City and Rebecca Gruchalla of the University of Texas Southwestern Medical Center in Dallas call the trial a “landmark” and endorse a skin-prick test for infants age 4 to 8 months who are at risk of peanut allergy. If the test is negative, start the baby on peanut butter at least three times a week for three years, they say. Mildly positive children, like many in the new study, should be given peanut butter initially with a doctor’s supervision. The new study “makes it clear that we can do something now to reverse the increasing prevalence of peanut allergy,” Sampson and Gruchalla conclude.

Editor’s note: This story was updated February 24, 2015, to correct the labels in the bar charts. The labels for the groups assigned to avoid peanuts or to eat peanuts were reversed. It was further updated on March 3 to clarify that peanut allergy rates have risen to up to 3 percent in the last 10 years, not grown from 1.4 percent to 3 percent.