Is it really possible that the rate of peanut allergies, like all food allergies, has been rising for the last 30 years because we aren’t training tolerance in babies?

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“Nobody is born tolerating peanuts,” says Dr. Brian Schroer, director of allergy and immunology at Akron Children’s Hospital. “Every baby needs to be trained to tolerate peanuts.”

Research, including the LEAP, EAT, and PETIT studies, has shown that feeding high-risk babies peanuts and eggs and perhaps other foods in infancy can reduce their risk of developing a food allergy to that food.

To better understand how babies can be trained to tolerate peanuts, let’s start by discussing what an allergy is — an immune system reaction to something harmless.

We’ll then explore the dual exposure hypothesis, which explains how your baby might develop an allergy.

Finally, we’ll take a look at how early allergen introduction may be able to stop the development of an allergy before it starts.

Your baby’s immune system is like the multilayered security system of a bank. There is a thick wall, silent alarms, and security officers to escort robbers out.

When customers walk in, the security system stays calm. When a robber bursts in, the security system locks the doors, the alarms go off, and officers spring into action.

Your baby’s “thick wall” is called the epithelial barrier. It is made up of the skin, the walls of the airways, and the walls of the intestines. Your baby’s silent alarms are antibodies. And your baby’s security officers are immune fighter cells (T cells, B cells, mast cells).

Allergies occur when your baby’s immune system goes haywire and reacts to grass, or cat dander, or a peanut instead of true harmful substances (pathogens). It’s like the bank’s security system reacting to a raccoon instead of a bank robber — both masked, one harmless.

All allergy diseases, including asthma, allergic eczema, food allergies, and environmental allergies, are what happen when your baby’s immune system keeps reacting to false alarms.

The epithelial barrier, our thick wall, is the largest immune organ we have. It covers our whole outer body and lines our throat, stomach, and intestines. The epithelial barrier is constantly exposed to bacteria, fungi, foods, pollens, clothing materials, and chemicals.

A baby’s immune system is doing almost all its learning and growing in the first years. During this time, the epithelial wall is getting set up and the alarms are learning when to go off.

When the epithelial barrier is cracked or weakened (by changes to the environment, pollution, or chemicals) during the immune system’s learning period, research indicates it may lead to lifelong immune mistakes.

Take the skin for example. If a baby’s skin barrier is broken, either because it is naturally dry (genetics), or because it was dried out (bathing with harsh soap), the skin cannot do a good job of keeping things out. Pollen and food, and worse, can cross the barrier when they shouldn’t.

Research exploring the dual exposure hypothesis theorizes that when harmless proteins like those in peanuts, eggs, or animal dander cross a baby’s cracked skin, the body can become sensitized to those proteins. “Sensitized” means that the body creates antibodies, or silent alarms, for those proteins.

If the skin is not healed and repaired while the immune system is growing and learning, that memory will get reinforced. According to this theory, later — when a child eats a scrambled egg, for example — the immune system’s memory will cause an allergic reaction.

This may explain why there is a strong association between eczema and developing food allergies. The more severe the eczema, the more cracks there are in the skin. The earlier eczema starts, the longer the body has to learn the mistake.

In one large 2015 study, 51 percent of infants with early-onset eczema who required prescription-strength treatment developed a food allergy.

Another theory is that this kind of exposure leading to sensitization instead of tolerance may also apply to the barrier of the stomach and airways.

A 2019 study suggested that when the gut microbiome is wrong, the intestinal barrier may get weaker, and even “leaky.” Proteins crossing the intestinal barrier could potentially create silent alarms that eventually lead to an allergy.

More than a decade ago, doctors realized that peanut allergy rates in Israel were not skyrocketing like they were in the United Kingdom. They asked a few hundred families in both countries to keep detailed daily diaries to find out what the Israeli families were doing differently.

The researchers uncovered that Israeli families were feeding their babies peanuts and other foods that commonly cause allergic reactions. British families, like American families, were avoiding wheat, eggs, peanuts, tree nuts, and more until their children were almost 2.

Thinking back on the immune system as a security system, doctors wondered “could Israeli parents be teaching the alarms not to go off?”

The doctors considered if regularly feeding babies certain foods from about 4 months old to 3 years old would teach the alarms to stay off. This period is when the immune system is learning and deciding what is good and what is bad — what is safe to eat and what to throw up.

They hypothesized that parents might be able to teach their baby’s immune system to make the right choices.

The Learning Early About Peanut (LEAP) study tested their hypothesis with children at high risk for peanut allergy (due to their severe eczema and/or egg allergy) and found that a training protocol of eating 2 grams of peanut protein 3 times a week, reduced the rate of peanut allergy by 80 percent.

A follow-up of the LEAP study children showed that the protection against peanut allergy lasted, even if children stopped eating peanuts after the study. This suggested that the key was consistent training during that 4 months to 3 years old window until a baby’s body made a final decision.

The LEAP study also showed that eating peanuts did not protect against other food allergies. So the Enquiring About Tolerance (EAT) study examined a protocol of feeding babies 1 to 2 grams of several proteins 2 to 3 times a week, and found that incorporating wheat, egg, and peanut did not disrupt breastfeeding while allowing for early introduction of other potentially allergenic foods.

Another study from 2017 showed that aggressively treating eczema and feeding baked eggs could help prevent egg allergy in high-risk babies, and an additional study published in 2021 showed that having a bit of cow’s milk-based formula every day could help prevent cow’s milk allergy.

Early allergen introduction, the practice of feeding high-risk babies a 2-gram serving of peanut proteins 3 times a week, is now an accepted way to train tolerance and possibly prevent a peanut allergy from ever developing.

Discuss your baby’s risk level and how to proceed with allergen introduction (including peanuts, tree nuts, eggs, and wheat) with your pediatrician or an allergist. But there are still some questions and some challenges.

For one, early allergen introduction every week, for months, is not easy. And it may not be necessary for all babies. For most babies the Centers for Disease Control and Prevention encourages caregivers to introduce foods in no particular order, beginning around 6 months.

If your baby is considered at moderate to high risk of an allergy it’s likely your doctor can help with recommendations. Some doctors recommend using commercially available products if that makes it more practical to get 2 grams of protein per serving, multiple times per week.

As for outstanding questions, there’s new research that continues to expand our knowledge of food allergy prevention.

A 2020 British study showed that overall diet diversity directly correlated with lower food allergy rates.

A diverse diet is defined as including four or more of the following seven groups of foods:

  • grains/roots/tubers
  • legumes/nuts
  • dairy
  • meat
  • eggs
  • fruit and vegetables rich in vitamin A
  • other fruit and vegetables

The risk of food allergy decreased by an additional 10 percent for every one of the groups a baby regularly ate by their first birthday.

Which is the more important part of training? Lots of different foods, the right serving size of each food, or the frequency of each food? We don’t exactly know.

Even though we don’t have an exact recipe for preventing allergies, we probably don’t need one. Around the world, we see that babies thrive under many different routines. Here’s what may be important.

Protect your baby’s epithelial barrier

  • Take as many chemicals and pollutants as possible out of their environment.
  • Breastfeed, if possible.
  • Do not bathe them with harsh soaps — stick to warm water and a gentle pat dry. If you see signs of eczema, talk to your pediatrician right away to get help soothing their skin.

Use early introduction to train tolerance

  • If your baby is exclusively breastfeeding, consider adding a bit of formula into their routine to train tolerance to milk.
  • Do not delay solid foods past 6 months old. Talk with your doctor about any concerns regarding starting solids.
  • As soon as your baby starts solids, begin to incorporate baby-safe versions of peanuts, tree nuts, egg, and wheat as part of a balanced diet. Nuts, even nut butters, and hard-cooked eggs are a choking hazard until after the age of 1 year.
  • If your baby is high risk, consult your pediatrician or allergist about whether testing is needed, how to begin, and how frequently to feed these foods to help prevent allergies.

We are learning more and more every few years about the immune system and how to help kids who have developed eczema, asthma, and food allergies. But this knowledge — how to prevent these conditions from ever starting — may be the most powerful knowledge we have.


Meenal Lele is founder of Lil Mixins. She has a chemical engineering and business degree from the University of Pennsylvania. After her world was rocked by her son’s eczema, food allergies, and asthma, Meenal began researching and working to end this epidemic. Meenal writes and speaks on the current state of science to help parents understand how they can protect their kids.