To keep your kids from developing an allergy to peanuts, should you give them nuts at an early age or withhold them? For years the debate has generated more heat than light, but today a landmark study led by King’s College London researchers offers some potent evidence that suggests giving peanuts to infants dramatically decreases the risk of developing an allergy to peanuts.



The researchers enlisted 640 children under the age of one to take part in a peanut allergy study. The researchers chose at random about half the kids to receive small peanut snacks each week until age five; they instructed the other half to avoid peanut products entirely. At age five all the children were given peanuts to test their reactions. The scientists concluded that early, regular introduction of peanut snacks can decrease the risk of developing peanut allergy by as much as 86 percent. “These results were remarkable,” says Matthew Greenhawt, research director for the University of Michigan Food Allergy Center, who was not involved with this study. Among kids who avoided nuts, 17.2 percent had developed allergies to peanuts; only 3.2 percent of the nut-eating kids became allergic.



All the 640 kids in study were at a higher risk of allergies to peanuts because of preexisting risk factors like eczema and known allergies to other substances; 542 showed no prior allergy to peanuts in skin-prick tests. In that group 13.7 percent of the peanut-avoiders and 1.9 percent of the peanut consumers had developed peanut allergies by age five. Eating peanuts was associated with an 86 percent reduction in peanut allergies.



Early exposure to peanuts even appeared to help a significant number of the 98 children in the study who tested positive on the skin-prick test in infancy. In that group 35.3 percent of kids who had avoided peanuts tested positive for allergies by age five, compared with 10.6 percent who had been eating peanuts. Including peanuts in the diet was associated with a 70 percent reduction in peanut allergies among kids who had positive test results at study entry.



However persuasive, results from one test may not be sufficient for making sweeping changes in policy, Greenhawt cautioned. “I think this is some great evidence kids should be getting peanuts earlier and I think we’re much closer to an answer that could change policy, but we need to make sure this can be replicated and can be generalized to other populations.”



To assess the implications of this study, published today in The New England Journal of Medicine, Scientific American spoke with senior study author Gideon Lack, head of the Department of Pediatric Allergy at King’s College.



[An edited transcript of the interview follows]:



What does this study mean for the hygiene hypothesis, a theory that suggests our modern, sterile environment contributes to the development of allergies?

I don’t think it has any positive or negative implications for the hygiene hypothesis. One thing to bear in mind is that all allergies have increased in recent decades, not just peanut. Our natural susceptibility to develop these allergies could potentially be explained by the hygiene hypothesis but that has not been established. It’s very interesting that in animal models oral tolerance to food such as egg will develop by feeding young mice egg very early on—usually a single dose is enough to help prevent allergies. But that only works in mice that have normal gut flora. If you take mice that are germfree, those that have a sterile gut with no commensal bacteria, the phenomenon of oral tolerance does not occur. So that may mean you need more than one factor to induce oral tolerance.



Based on your findings, do you think there should be changes in the recommendations for how to combat peanut allergies?

In 2008 recommendations for the avoidance of allergens were withdrawn based on lack of evidence. But while the guidelines on avoidance were rescinded, they weren’t replaced by guidelines encouraging consumption so the change in 2008 did not have a substantial effect in the children I see in my clinic. They are still pretty much universally avoiding peanuts if they come from high-risk families like those with eczema.



I think now, on balance, recommendations need to be carefully considered by local public health guideline-making bodies in countries where peanut allergy is a problem. I don’t think it makes sense to be changing or introducing policies in countries where peanut allergy is not a problem, like parts of Africa and Asia. This will have to be left up to local pediatricians, allergists and public health physicians in those countries.



All the kids in your study have severe eczema or egg allergy. Why is that? What’s the relationship between those conditions and peanut allergy?

It was a recruitment strategy because we wanted to target a group of children that have a high risk of having peanut allergy. Two percent of kids in the general population will develop peanut allergy. Kids with egg allergy or eczema, however, have about a 15 to 20 percent chance of developing peanut allergy. If we chose a study group that wasn’t at a heightened risk of developing peanut allergy we would have had to enroll thousands of kids in our study to see a statistically significant change. Our statistical power calculations allowed us to enroll 640 children here and that was already a large task.





What would you recommend to parents now, based on your findings? Should they be feeding peanuts to their kids?

Among low-risk kids that account for 80 to 90 percent of population—those that don’t have eczema in the first six months to year of life and don’t have any evidence of food allergies—I would recommend that these children eat peanut protein or peanut in various forms, depending on the culture. Low-risk children should start eating peanut butter as soon as weaning is established. You don’t want peanuts to be the first food because if the kid is gagging or choking, it could represent allergic manifestation but it may also just indicate the child hasn’t developed the coordination to eat solid foods.



Higher-risk kids, those with any manifestation of eczema or food allergy, should see an appropriate health care provider, which could be an allergist or a pediatrician, and have skin prick testing done for peanut as soon as these high-risk symptoms develop. If the child tests negative, the child should be encouraged to eat peanut at home. If the skin test is a small positive, like it was for some of the kids in our study, then the children should have their first exposure or consumption of peanut under medical supervision; and if they tolerate it they should be encouraged to continue to have peanut regularly in their diet for at least the first three years of life. Based on the evidence we have, one could arguably say the first five years of life. Kids in our study that tested positive and developed a wheal [small circles of inflammation that indicate sensitivity] of one millimeter to four millimeters were included in our analysis.



Will the kids without peanut allergies have to keep taking peanuts from now on in order to ward off peanut allergies?

Kids who graduated from our study have been asked to completely avoid peanuts for 12 months as part of a separate study. Then they will be reassessed to see if they remain tolerant of peanuts or have acquired peanut allergy.



What implications do your findings have for combating other allergens?

This method could apply to other allergens—at least in theory—but I would caution our findings do not indicate it will definitely do so. There are ongoing studies looking at other allergens. The EAT [Enquiring about Tolerance] Study, for example, is looking at exclusive breast-feeding for six months of life compared with early introduction at three months of age to fish, egg, dairy products, wheat, sesame and peanut. That study is ongoing and should be completed in the next six-month period.



We can’t say it’s a foregone conclusion this would work for other allergens; we have to wait for their results.



Are peanuts a unique allergen?

Every allergen is unique in that it has a unique protein structure. What is special about peanuts but not unique to peanuts is that multiple allergenic proteins are within them. Peanuts are highly resistant to heat, digestion and changes in pH. It’s allergenicity is increased by roasting rather than decreased and therefore it’s a very potent allergen. But having said that, the same does apply for a number of other allergens but perhaps not all to the same extent.



How did you choose the amount of peanuts kids consumed in this study?

It was chosen on the basis of observational studies of what kids in Israel are eating. We had observed several years ago that kids in Israel did not develop peanut allergies nearly as often as Jewish children of similar ancestry in the United Kingdom and that the Israeli children were eating peanut snacks from an early age—typically two grams to six grams a week. We chose that upper limit in our study.



Your study focuses on fighting allergies from infancy. Does this approach have relevance for adults who have already developed peanut allergies?

No, we have looked at prevention, we have not looked at treatment—therefore nothing we have shown or demonstrated can be extrapolated to treatment.



You did not include kids who had a large positive reaction to the initial skin prick test (those larger than four millimeters). Do you think this peanut exposure regime would work on them?

It’s very hard to say. For a large number of these children, probably not because the likelihood is many of them would have already been allergic. Intervention only works if you don’t have the disease, and we suspected a high number of these kids were already allergic.



