For decades, American parents have been vigilantly protecting their babies from a ubiquitous threat: peanuts, a top cause of anaphylaxis (a severe allergic reaction) and death due to food allergies. Some airlines prohibit passengers from eating peanuts. Many schools have banned peanuts as well as tree nuts in school lunches. Up until 2008, guidelines from the American Academy of Pediatrics urged parents to avoid exposing their infants to peanuts until they reached the age of 3.
Yet, in the U.S., peanut allergies appear to have quadrupled in the last 13 years. Tree nut allergies have also increased, not just among children in the U.S., but also in the U.K. and Australia. Why is that, and what can parents do to protect their children? A surprising answer is causing many doctors to rethink how we approach nut allergies.
In a paper published in 2008 in the Journal of Allergy and Clinical Immunology researchers in the U.K. found that peanut allergies were 10 times more common among Jewish children in the U.K. compared with Jewish children in Israel. One theory: In Israel, parents feed a popular snack food containing peanut butter, called Bamba, to their children starting when they’re about seven months old. Could early exposure to peanuts actually help prevent children from developing the allergy?
To find out, some of the same investigators collaborated with the University of California, San Francisco, and the National Institute of Allergy and Infectious Diseases (part of the National Institutes of Health) to study hundreds of infants who were at heightened risk for developing a peanut allergy because they had severe eczema or egg allergies. One group of babies ate small amounts of food containing peanut protein (2 grams, the equivalent of 8 peanuts) at least three times a week until they were five years old. The other group avoided peanut products for the same time period.
The results—published in 2015 in the New England Journal of Medicine—showed that infants who ate peanuts were 81 percent less likely to have a peanut allergy by age 5. Only 2 percent of the peanut-eating babies developed the food allergy, compared with about 14 percent of those who avoided peanuts. And among those who already showed a sensitivity to peanuts at the start of the study, only 11 percent developed an allergy, compared to 35 percent of the babies who avoided peanuts.
The type of exposure to peanuts matters most
What accounts for these results? The researchers believe that being exposed to peanuts early in life by eating them creates an immune tolerance to the protein that triggers allergic reactions. That may be what protects the Israeli children. Jewish kids in the U.K. and U.S., where early peanut eating isn’t advised, are more likely to get their first exposure to the peanut protein on their skin—through dust in the air or by touching the hand of someone who has eaten peanuts. Skin exposure can lead to a different and sometimes more vigorous immune response, which creates the allergic reaction.
Do young children have to keep eating peanuts in order to keep the allergy at bay? What happens if they stop eating them? To answer this question, the researchers had the children in the study stop eating peanut products at age 5 and abstain for one year, until they were 6 years old. There was no significant increase in peanut allergies.
Important unanswered questions
Researchers acknowledge that much more research is needed to address some important unanswered questions:
- Could children remain free of peanut allergy throughout their lives if they eat peanuts early?
- Do infants need to eat the equivalent of 8 peanuts three times a week for five years—or can they eat less for a shorter amount of time and still be protected?
- Can pregnant women pass on some immunity to their unborn babies by eating peanuts and tree nuts during pregnancy?
A 2014 study published in JAMA Pediatrics hints at an answer to the third question, though more study is needed. Using data from the large, ongoing Nurses Health Study II, researchers found that mothers who ate peanuts and tree nuts during pregnancy were less likely to give birth to children with peanut or nut allergies, especially if the women ate nuts often, at least five times a week. But it's not clear from the data whether the protection was due to the mothers' consumption of nuts during pregnancy, or passed on genetically.
Regardless, based on the recent studies, numerous major medical organizations—including the American Academy of Allergy, Asthma, and Immunology and the American Academy of Pediatrics—published a consensus statement saying that parents should not delay introducing foods with peanuts into the diets of their children beyond 4 to 6 months of age.
However, if your doctor advises you to introduce the food, do so with care. If your baby is at high risk for peanut allergy because she has severe eczema or egg allergies, introduce a small amount of peanut-containing food to your child at the allergist’s office. Be sure the doctor is present. Most allergic reactions to peanuts occur the first time a baby eats the nuts. And never give whole peanuts to young children; they’re a choking hazard.
Children who are already allergic to peanuts should never be given the nuts. Once the allergy is established, eating peanuts will not turn things around, and exposure can be life-threatening. While 15 to 22 percent of kids outgrow their peanut allergy by the time they’re teenagers, it is a lifelong problem for most.
Also see Allergies and Allergy Tests.