The news last month of a clinical trial showing that infants at a high risk for peanut allergies were much less likely to actually develop these allergies if they were fed regular peanut snacks made me want to reach for a spoonful of peanut butter to shove down my 7-month-old’s throat. But then visions of hives and red puffy welts danced in my head and I reconsidered. Like many parents, I have long been under the impression that the best way to prevent food allergies in kids is to delay giving them allergenic foods such as peanuts and eggs until they’re older. So before presenting my daughter with a bowl full of Jif based on a single finding, I decided to dig into the research.
The simplest way to sum up my conclusion is to say that my daughter tried her first bite of peanut butter last week. She made a stink face but was otherwise fine. As it turns out, the outcome of the recent trial, which was covered by many news organizations as if it shattered current established dogma, was actually not terribly surprising if you’ve been following current advice and research on food allergies. It’s been clear for a while that waiting a year or longer to feed your child peanut butter and eggs is useless at best. Some research even suggests that the earlier you introduce these foods the better—4 months, in other words, may be better than 6 months, even though the American Academy of Pediatrics’ official recommendation is to wait until 6 months to give babies any solid food. Even crazier: If your kid seems a little sensitive to a particular food—perhaps dairy gives her a minor rash around the mouth or loose stools—the worst thing to do may be to stop giving her that food.
First, let me quash the widely held notion that delaying the introduction of allergenic foods to babies is a good idea. That approach was based in part on the flawed notion that it’s smart to let an infant’s gastrointestinal and immune systems “mature” for a while so they can better handle allergenic foods, and some studies from the 1990s did support it. But then contradictory studies began flooding in, and scientists now believe that exposing the gastrointestinal system to an allergen early in life is unlikely to cause an allergy. It probably does the opposite. (More on that later.)
In light of the changing tide, back in 2008, the American Academy of Pediatrics published new recommendations that reversed its old dogma. “Although solid foods should not be introduced before 4 to 6 months of age,” it wrote, “there is no current convincing evidence that delaying their introduction beyond this period has a significant protective effect.” Unfortunately, a lot of pediatricians haven’t gotten the memo and are still giving parents outdated advice, which may explain why everyone was so shocked by last month’s trial results. Also, in 2012, the AAP confused things further when it started telling parents to wait until 6 months to feed babies any solid food, a recommendation that was designed to encourage mothers to breastfeed for longer.
Here’s the thing, though: When it comes to preventing food allergies, research is starting to suggest that it may be better to give babies allergenic foods closer to 4 months than 6 months. You should never give babies under the age of 4 months solid food, and you also shouldn’t force solid food on a baby who isn’t showing signs of being ready. But once your infant does seem ready, you can go for it—give her eggs, peanut butter, strawberries, the works (though be sure to read the caveats below). One recent Finnish study found that babies introduced to solid foods such as oats, potatoes, and meat before the age of 6 months were less likely to develop food allergies. Another study by some of the same authors found that babies—particularly those with a family history of allergies—who were fed a larger variety of solid foods at 4 months developed fewer skin allergies than those fed a smaller variety at 4 months. Another study reported that babies who were fed cereal grains before they hit the 6-month mark were less likely to develop wheat allergies than babies who were first fed grains after 6 months. And a rather shocking and controversial 2010 study reported that newborns who were given cow’s milk formula within two weeks of birth had 19 times lower odds of developing a cow’s milk allergy compared with newborns who were not. “Solid food introduction from 4 months of age, including a wide range of healthy foods and potential food allergens such as eggs, peanuts, and fish, is our current best advice,” says Debbie Palmer, head of the Childhood Allergy and Immunology Research team at the University of Western Australia, who has published extensively on the topic.
The American Academy of Allergy, Asthma & Immunology recently published detailed recommendations on this front, and its advice is basically this: Breastfeed your baby exclusively for the first 4 months of life; if you can’t, and your baby has a family risk of allergy, consider using a hydrolyzed formula. Then, regardless of whether your baby has a family risk of allergy or not, feed your 4-to-6-month-old “complementary” foods first, one at a time, waiting a few days in between, while continuing to breastfeed or feed formula. These include rice and oat cereals, vegetables, fruits (including berries—they’re fine), and certain meats. If your baby has tried and done well with a few of these, start giving her tastes of allergenic foods such as peanut products and eggs. (But before you start giving your baby Cracker Jacks, there are a few important caveats: Never feed babies whole peanuts, because they can choke on them. If your baby has a sibling with a food allergy, you may want to consult an allergist before giving her those same allergenic foods. And babies still shouldn’t be given cow’s milk as their main drink before their first birthday because it’s too low in iron and may lead to anemia.)
So how does this approach work? After all, you have to be exposed to something repeatedly in order to become “sensitized” to it and develop an allergy. That’s part of the established allergic cascade. So why would eating something repeatedly prevent allergies? As it turns out, how a person is exposed to an allergen really matters. Most scientists now believe, based on what is called the dual-allergen-exposure hypothesis, that a person becomes allergic to, say, peanuts by being exposed to peanut proteins through the skin. (If you have peanut eaters in your home, peanut proteins are probably all over your house, no matter how frequently you vacuum.) Eating peanuts, on the other hand, helps to promote tolerance to them, thereby decreasing allergy risk. The epidemiology of peanut allergies supports this idea. In countries where peanuts are not regularly consumed, such as in parts of Europe, peanut allergies are rare, because babies are less likely to become sensitized to peanut proteins through the skin. In the Middle East and Africa, where peanuts are regularly consumed by everyone but babies also eat peanuts at a young age, rates of peanut allergy are also low, because babies become sensitized to peanuts but also tolerant of them. It’s really only in the countries where peanuts are a food staple and yet babies don’t regularly eat them—such as in the U.S. and in Canada and in the U.K.—that peanut allergies are so common, because infants become sensitized but not tolerant. In other words, here in America, the old recommendation to “delay the oral introduction of peanuts and eggs was quite possibly the worst approach,” Palmer says. Oops!
This theory suggests something else interesting, too: People who are allergic to a food might become less allergic the more they eat it. And actually, this is one of the findings from last month’s trial. At the beginning of the trial, researchers gave peanut allergy skin prick tests to all the enrolled infants. Even if the infants tested positive—indicating that they were probably allergic to peanuts—the researchers advised the parents to give their babies small amounts of peanut snacks regularly, as long as they did not have dangerous reactions to it in an initial food challenge, until their kids reached their fifth birthday. The researchers told a second group of parents whose babies had tested positive on these skin prick tests to avoid peanuts until age 5. Then, years later, the researchers gave allergy tests to all the 5-year-olds and found that those who had regularly consumed the peanuts were one-third as likely to be allergic to peanuts compared with the kids who had been told to avoid them.
These findings suggest that if your children have a mild reaction to a food—maybe it makes them break out in a mild rash or causes digestive troubles—then “they would be best to continue to include having small amounts on a regular basis,” Palmer says. (Of course, you should consult an allergist too.) A number of other small studies support this idea, known as “immunotherapy,” for overcoming various types of food allergies, but it’s still unclear how long the effects last—it may be that people have to keep consuming the allergen regularly to avoid becoming allergic again—and exposing allergic individuals to their offending allergens can, of course, be risky. By the way, if you do suspect your kid has a food allergy, go get him tested—one study found that only 14 percent of parentally diagnosed food allergies are actual food allergies. Plus, those that do exist often resolve themselves over time, so consider getting your child retested once a year. There’s certainly no reason to keep peanut butter out of the house if you don’t have to.