Consuming peanuts in infancy appears to lessen, not increase, a child’s risk of developing a peanut allergy later, British researchers report in the November Journal of Allergy and Clinical Immunology.
The findings clash with some pediatric practices of the past decade, in which parents have been told to avoid feeding peanut products to their infants. In contrast, the new study suggests that early exposure by eating peanuts — in the form of peanut butter — might induce tolerance and head off the aberrant immune response that underlies an allergic reaction.
“This work is extremely thought-provoking and raises the possibility that an approach of trying to avoid peanuts may be the wrong thing to do,” says Robert Wood, an immunologist and pediatric allergist at Johns Hopkins University in Baltimore.
Allergist Gideon Lack of King’s College London and his colleagues distributed food allergy questionnaires to thousands of families in Britain and Israel in 2004 and 2005. The research team analyzed nearly 9,000 responses that parents returned, which contained data on roughly 4,000 Jewish children in North London and 4,600 Jewish children in Tel Aviv.
The researchers chose Jewish children in both countries to limit genetic differences between comparison groups.
Peanut allergies showed up in 0.17 percent of the Israeli children and 1.85 percent of the British children, an 11-fold increase in risk. Even after the researchers accounted for age differences between the groups, and for the prevalence of other food allergies and allergic reactions such as rashes or asthma, the British kids were still nearly six times as likely to have a peanut allergy. Among primary school children the risk was nearly 10-fold.
To assess what “first foods” are given to babies in England versus in Israel, the researchers gave questionnaires to mothers visiting clinics with children ages 4 to 24 months — distributing 99 surveys to Israelis and 77 to Britons. These surveys detailed when the babies first received cow’s milk, peanuts, other nuts and eggs.
The questionnaires revealed that early peanut consumption was more common in Israel. At 9 months of age, 69 percent of Israeli babies had started eating some form of peanuts, whereas only 10 percent of children in Britain had. There was little difference in the age of introduction of the other foods.
“I think there is enough here — even from trying to compare these two different populations — to suggest that peanut avoidance practices in most of the industrialized societies now need to be re-examined,” says Wesley Burks, an immunologist and pediatric allergist at Duke University in Durham, N.C.
Peanut allergy in kids has grown in recent decades in Europe, Australia and the United States, where fear of the allergy has discouraged peanut butter as an early food, the authors note.
In 2000, the American Academy of Pediatrics recommended withholding peanut products until a child had reached three years of age. But in 2008, based on mixed results in ongoing studies, the Academy rescinded that recommendation and reverted to its standard recommendation for introducing non-breast milk foods to infants — wait until only four to six months of age.
Nonetheless, similar warnings remain in place in Britain and Australia.
Meanwhile, infants commonly consume peanut products in the Middle East, Africa and Southeast Asia. In all places, peanut allergy is rare, the authors point out.
The cause of peanut allergy is unknown, but there are theories. It’s widely accepted that genetic predisposition plays a part. But genes wouldn’t account for the recent rise in peanut allergies, since genetics don’t change rapidly, Wood says.
A fascinating causal theory for peanut allergy arose in a 2003 study by Lack and his team. They found that preschool children who were allergic to peanuts were much more likely as infants to have been treated with skin lotion containing peanut oil than were children who didn’t have the allergy. The researchers hypothesized that exposure to peanut protein through the skin laid the foundation for an aberrant immune reaction in some children that resulted in allergy.
The British team started recruiting families in 2007 to participate in a long-term study of 640 children under age 11 months, in which some would randomly be assigned to eat peanut products and others wouldn’t. When the children reach age 3, the scientists will assess who had developed a peanut allergy. Results are expected by 2014.