“If you’re worried about allergies, wait to introduce foods.”
Have you ever heard that?
Well, not anymore. Medicine has seen a huge shift in how we think about preventing food allergies.
It used to be believed that babies should start potentially allergenic foods as late as possible. Today, for certain foods, we think that introducing them at the right time may actually help prevent allergies from developing.
Our thinking has changed this much in only about 10 years!
Maybe you’ve experienced this yourself: the advice you got with your first baby isn’t the same as what you’re hearing with your second. Parenting “common sense” changes more than you’d expect.
Today, I want to talk about how the conventional wisdom on food allergies has changed, and why.
“Wait as Long as Possible” Used to Be the Right Answer
Not long ago, the thinking was that to prevent food allergies, you should hold off on allergenic foods like eggs for as long as you could.
If eating a food can cause an allergy, then just don’t feed it, right? In a way, that’s a pretty natural line of thought.
In fact, in 2000, the American Academy of Pediatrics (AAP) suggested delaying the introduction of foods like eggs for babies at high risk of allergies.
But later studies failed to show solid evidence that delaying foods actually prevents food allergies. In 2008, the AAP changed course, stating there was no convincing evidence that delaying the introduction of specific foods prevents allergies.
Then, in 2015, a study came out that would completely change the landscape of food allergy prevention.
2015: The Peanut Study That Changed Medicine
In 2015, a research team in the UK published groundbreaking results on preventing peanut allergy.
The study, known as LEAP, followed 640 infants at high risk of peanut allergy, babies with severe eczema, an egg allergy, or both. One group regularly ate peanut-containing foods. The other group avoided peanuts completely. The researchers then checked who had developed a peanut allergy by age 5.
The results were striking.
Among children who had a negative peanut skin test at the start of the study, 1.9% of those who ate peanuts had developed a peanut allergy by age 5. In the group that avoided peanuts, it was 13.7%.
The kids who ate peanuts had a dramatically lower rate of allergy.
It was the exact opposite of what everyone had assumed: “If you’re worried about allergies, hold off on the foods most likely to cause them.”
Following this study, the U.S. updated its peanut allergy prevention guidelines in 2017. For infants with severe eczema or egg allergy, and after an evaluation by a healthcare provider, introducing peanut-containing foods at around 4 to 6 months of age is now recommended.
“I’m worried about allergies, so I won’t feed it.”
Research showed that this isn’t always the right call.
So Why Would Eating a Food Help Prevent an Allergy?
This is the most fascinating part of the story.
A food allergy happens when the immune system, which is supposed to protect us, mistakes a harmless food for an enemy.
So why would that mistake happen? One of the key factors is how the immune system works in two different places: the skin and the gut.
Our skin acts as a barrier that keeps foreign substances out. But when that barrier is broken down, for example by eczema, food proteins floating around in our environment can slip in through the skin more easily.
When that happens, the immune system may flag the food as a threat and get ready to launch an allergic reaction. This is called skin sensitization (or percutaneous sensitization).
On the other hand, when food enters through the mouth, a different system kicks in, one designed to accept food. The gut helps regulate the immune system so that it doesn’t overreact to things that are normally harmless, like food. This is called oral tolerance.
In other words, the same food can lead to sensitization when it gets in through the skin, yet when it’s eaten, the immune system may learn that “this one’s not an enemy.”
Here’s one way to picture it: when a food sneaks in through the skin, the immune system can go on high alert. When it arrives through the gut, there’s a built-in system that says, “Don’t worry, this one’s safe.”
This is one of the big reasons our approach to preventing food allergies has changed so much.
It used to be thought that avoiding allergenic foods was the way to prevent allergies. But as research progressed, we’ve learned that, for certain foods, eating them at the right time may lower the risk.
Of course, this doesn’t mean every child should eat every food as early as possible. And it’s dangerous to give a food on your own if your child already has an allergy to it. Still, the idea that we can build up the immune system by eating the right foods at the right time, not just protect by avoidance, was a major turning point.
And there’s one more thing we shouldn’t forget: treating eczema.
If a weakened skin barrier plays a role in developing food allergies, then properly treating eczema and keeping the skin healthy matters too. Avoiding foods isn’t the only way to prevent allergies.
Japan Joined In: The Egg Study That Made Waves
The peanut research changed how we think about preventing food allergies.
In Japan, an important study on preventing egg allergy followed.
It’s called the PETIT study, published in 2017.
In this study, infants with eczema had their skin condition properly treated while also eating heated egg, starting with tiny amounts and increasing step by step.
The results: at 1 year old, 8% of the babies in the egg group were diagnosed with an egg allergy, compared with 38% in the placebo group.
So a study conducted in Japan also showed that, under specific conditions, early introduction of egg could help prevent egg allergy.
Based on this, the Japanese Society of Pediatric Allergy and Clinical Immunology issued recommendations on preventing egg allergy in 2017.
But there’s an important caveat. What this study tested was a combination of eczema treatment and gradual egg introduction carried out under a medical research protocol. It doesn’t mean you should start feeding your baby eggs early on your own, with a do-it-yourself approach.
Still, one thing is clear: thanks to the peanut and egg research, how we think about preventing food allergies has changed dramatically.
Just 10 Years, and Everything Changed
My son started solid foods about 10 years ago.
When I compare the parenting “common sense” of that time with today’s, I’m amazed at how much our approach to preventing food allergies has changed.
From “If you’re worried about allergies, delay the foods,” to “For certain foods, starting at the right time may help prevent allergies.”
We used to think that avoiding foods was how you prevented allergies. Now we know that eating them might help the immune system learn, and could lower the chance of an allergy developing. It really was a complete about-face.
My son can’t eat eggs or wheat. Now that he’s 10, we’re still living with his food allergies every day. That’s exactly why I hope that this growing body of research opens up new possibilities for the children who are yet to be born.
When Parenting Is Behind You, Do the Updates Stop Coming?
When your kids are babies and toddlers, you’re surrounded by parenting information: well-baby checkups, baby food classes, notices from your local government, and more.
But as your kids grow up, those touchpoints fade away.
Even as research moves forward and new findings pile up in the medical world, that information doesn’t reach everyone, in every generation.
If you’re raising a baby right now, you may well come across the latest information. But what about people who raised their kids 10 or 20 years ago?
They may still believe that what was “common sense” back then is still true today.
It’s not just food allergy prevention. Medical wisdom changes as research advances.
In just 10 years, our thinking about preventing food allergies has changed this much.
Isn’t medical progress amazing?
So that’s the story of the “new rules” of food allergy prevention.
Whether you’re raising little ones right now, your kids are all grown up, or you’re about to start your parenting journey:
“Wait, that’s how it works now?”
I hope we can share that moment of surprise together.
