Learn about the dual allergen exposure hypothesis, why this hypothesis shows that giving your baby the "peanut butter kiss" is a bad idea. 

Many parents have heard about the "peanut butter kiss" as a possible way to introduce food allergens. The "peanut butter kiss" involves spreading peanut butter on your lips, then kissing your baby on their lips as a way to expose them to peanuts. 

But the "peanut butter kiss" is a bad idea. Based on what scientists call the dual allergen exposure hypothesis, this kiss won't work, and may actually increase your baby's peanut allergy risk.

The "peanut butter kiss" may actually increase your baby's peanut allergy risk.

Today, we'll break down what parents need to know about the dual allergen exposure hypothesis, why the "peanut butter kiss" is a bad idea based on this hypothesis, and why you need to feed baby peanut early and consistently.

What is the dual allergen exposure hypothesis?

According to the dual allergen exposure hypothesis, exposing baby to peanuts on the skin may actually increase your baby's peanut allergy risk. If allergens like peanut proteins pass through your baby's skin barrier often enough, they may lead your baby to develop an allergy. 

Having your baby eat foods containing peanut early and often is key.

As Dr. Gideon Lack explains, how these two different types of exposure---skin and eating---balance out determines whether your baby will have a peanut allergy.

The Dual Allergen Exposure Hypothesis and Eczema Babies

The dual allergen exposure hypothesis may explain one reason why babies with eczema are at the highest risk for food allergies.

Eczema babies have a damaged, compromised skin barrier. It's a lot easier for common food allergens to pass through their skin barrier. 

When eczema babies' skin touches peanut proteins, like peanut residue on a high chair or peanut oil in a cream, their broken skin barrier easily lets the peanut proteins through. So, they end up with more "negative" exposure to peanut than babies without eczema.

This is why it's especially important for eczema babies to eat peanuts (and other common food allergens) early and often. Eating peanuts early and often helps balance out all the "negative" peanut exposure they'll likely get through the skin.

Dual Allergen Exposure: Why the Peanut Butter Kiss Is A Bad Idea

The "peanut butter kiss" involves spreading peanut butter on your lips, then kissing your baby on their lips. But when your baby is exposed to peanut on their lips, that's a type of exposure on the skin. 

So, the peanut butter kiss may actually increase your baby's peanut allergy risk.

And if your baby has eczema, the peanut butter kiss is an even worse idea, because of baby's compromised skin barrier.

Babies need to be exposed to peanut in the mouth and GI tract (by eating), not on the lips and face.

How to Introduce Peanuts: Feed Baby Peanuts Early and Often 

Thanks to landmark clinical studies, including the LEAP study, we know that feeding your baby peanuts early and often is the best way to introduce allergens. But what exactly counts as feeding your baby peanuts early and often? According to the LEAP study, you'll need to start as early as 4 months of age, and sustain exposure for several months.

Learn more about the LEAP trial from this 1 minute video from the New England Journal of Medicine:

Starting around 4 months of age, babies enter a critical window. This window is thought to close around 11 months of age, but may close earlier. So, the sooner you start feeding baby peanuts after they turn 4 months old, the better.

But feeding your baby peanuts just once or twice during this period is not enough. The LEAP study shows that feeding your baby peanut 2-7 times a week for at least 3-6+ months is just as important as starting early. 

When feeding baby peanut, avoid whole peanuts, chunky peanut butter, and any peanut butter that isn't thinned with liquid, so baby doesn't choke.  Whole peanuts, chunky peanut butter, and unthinned smooth peanut butter are choking hazards. Learn more about feeding your baby peanut here.

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