EP 18: Allergen Introduction for Babies: What the Science Says About Timing Prevention

If the idea of introducing peanut butter to your baby sends your heart rate up — this episode is for you.

As a pediatrician and registered dietitian, I've sat across from families who are genuinely terrified of allergen introduction. Their fear makes complete sense. But fear doesn't get the final vote. A plan does.

In this episode, I walk you through two real families from my practice, the landmark science that completely changed how we introduce allergens, and exactly what to do based on your baby's individual risk — so you can move forward with confidence instead of anxiety.

In this episode:
✔ Why the old "delay allergens" advice tripled peanut allergy rates — and how the science did a full 180
✔ The LEAP trial: what it found, why it matters, and what 86% risk reduction actually means for your family
✔ The dual allergen exposure hypothesis — why your baby's skin is the real risk factor (not family history alone)
✔ Eczema and food allergy: what the connection is and why I treat eczema aggressively from the very first weeks
✔ Exactly how and when to introduce peanut butter and egg at home — by risk category
✔ Myths I hear every week that have no evidence behind them — including breastfeeding, hypoallergenic formula, and pregnancy diet
✔ What to do if YOU have a food allergy and you're terrified of passing it to your baby

Risk categories covered:
→ No eczema / no family history: introduce at home around 6 months, no testing needed
→ Mild to moderate eczema: introduce early at 4–6 months, no testing needed, focus on skin care first
→ Severe eczema: consult your pediatrician and/or allergist before introducing; testing may come first

Roberts G, Bahnson HT, Du Toit G, et al.  J Allergy Clin Immunol. 2023;151(5):1329-1336.

Logan K, Bahnson HT, Ylescupidez A, et al.  Allergy. 2023;78(5):1307-1318.

Greer FR, Sicherer SH, Burks AW.  Pediatrics. 2019;143(4):e20190281.

Islam N, Chu AWL, Sheriff F, et al.  JAMA Pediatrics. 2026 (published online Feb 9, 2026)

Wang HZ, Hayles EH, Fiander M, Sinn JK, Osborn DA. Cochrane Database Syst Rev. 2025;6:CD006475.

Du Toit G, et al.  New England Journal of Medicine. 2015;372(9):803–813.

PreventAll Trial Horimukai K, Morita K, Narita M, et al. J Allergy Clin Immunol. 2014;134(4):824–830.

Dual Allergen Exposure Hypothesis Lack G.  J Allergy Clin Immunol. 2012;129(5):1187–1197.

Early Skin Moisturization & Eczema Prevention Simpson EL, Chalmers JR, Hanifin JM, et al. J Allergy Clin Immunol. 2014;134(4):818–823. 

For education purposes only- consult your medical care provider for personalized recommendations.

NEW COURSE! "Read the Pattern: Feeding Your Baby 0–4 Months" — because a healthy relationship with food starts earlier than most people think. Course Link!

Transcript

SPEAKER_00 0:00

I'm not telling you all this to scare you. I'm telling you this because I want you to walk away today with something useful because the fear is real. The history is real. Your family's experience is real. And now we have tools that we didn't have 20 years ago. We can have a plan with evidence. Welcome to the Nutrition for the Early Years podcast with Dr. Liz, your guilt-free guidance for feeding your family. This podcast is for folks who are craving better nutrition for their kids, but are tired of the whiplash of nutrition claims and diet culture influence. You're reading labels, paying attention to ingredients, but you still doubt yourself. And for good reason, food goes deep, and often we fear making costly mistakes that as parents we hope to prevent. If you're ready to explore the ins and outs of your child's actual nutrition needs and nourish the whole child from the inside out, hang with me, Dr. Liz Daniels. I'm a board-certified pediatrician plus registered dietitian, and we're going to dig deep into real deal nutrition science, honest talk about barriers to health, and real stories that I help address. So let's dig in. And today we are going to talk about allergenic introduction, but we're going to do it through maybe a lens you haven't quite thought of before. So specifically, we're going to talk about who needs to worry, what the science says about prevention, and maybe most importantly, why your fear about introducing allergens is valid and why it doesn't get to be the one making the decisions for you and your baby. I want to start off a little differently though today. I actually want to tell you like tale of two families kind of scenario, real families. Families that I have been in the room with many times and have heard their concerns, walked them through and seen the outcomes of each of their stories. And we're also going to talk more about the data because the data really matters. And I'm going to give you a lot of it today, mainly because I know you can handle it. And it's genuinely exciting that we have this much research guiding how we can support babies' lives and things that we actually know now, really good things, actionable things that we didn't have the research for decades ago. And so this is really an amazing opportunity. If you know anyone who lives with a food allergy, you already understand why this matters. Because food allergies disrupt lives. They can disrupt relationships and they can interfere with our family dinners, school lunches, travel, spontaneity. And really they could just create a baseline level of vigilance that never really turns off. And that gut health piece, you know, like we could do even a whole other series on that, which we probably should. But today I'm going to go through these two family stories and the research that guides us so that you can decide what's best for your family. Okay, story one. I had a mama who had experienced a lot of food sensitivities and gut health struggles as a child. She was always in the school nurse office and was often told it was kind of just a stomach bug or things were going on. And, you know, they really couldn't figure out what was going on. Labs were normal for the most part, just never really knew what was causing her discomfort. And then finally got answers and she realized that it was actually food sensitivity. So nothing triggered on an allergy standpoint, but symptoms completely resolved when her diet changed. And that was evidence enough to know this really mattered for her. And she got pregnant. She was already eating everything organic as it was, but then it became heightened and she started reading every label. And in the pregnancy, it sort of became pretty consuming to her. Um, but doing everything she could to really protect her baby and have a different start. I get it. I totally get it. And when you've been through something painful and you have a chance to try to protect your baby, you will do it and you should. So we met when her baby was brand new. And probably a couple of visits in, I started hearing these stories that mom had experienced when she was young. So when it came time to introduce solids, you know, we had lots of conversation, deep conversation about this. And she said, okay, I just I know that I need to do these things. I know I need to introduce allergens. I'm just really scared. And we would go through and make plans and keep trying to introduce things, but I will say her fear was real, but it took a long time for us to actually get those allergens introduced. And when we did, it was pretty inconsistent because there was just so much anxiety, but everything had to be in the right environment. There had to be enough, you know, security blanket supports in place for her to do them. And her baby did okay. Like it really, she really never had any problems. But at the end of the day, the thing that I noticed is that her fear began organizing itself around food way before the baby even started solids. And that's worth noticing and mentioning. I call it pattern passing, the way our own food history can quietly shape the feeding environment we create for our kids before they even pick up a fork. And it's a conversation for another episode, but I just want to plant that seed today. And and while she had a scenario that was really scary and she was doing what she could, there still were some interruptions there. And I just think about how much easier that road could have been for her with some more support around navigating that fear. Okay. Now, second family. This couple came to me for an expectant parent visit. The question was okay, how do you recommend we introduce allergens? Because as a mom, I have anaphylaxis with peanuts, and it is a big deal to me. In this situation, we're talking about a mama who had experienced anaphylaxis multiple times. She knew what it felt like for her body to go into shock. And now she was pregnant and terrified that, you know, this would happen to her daughter. I am so proud of this family. We talked about it at not only the prenatal visit, but the newborn visit at two months. And she was actively working with her own medical team to support herself through it. She knew that her history was going to make this harder and she wanted to get help. And I want to say that again. She got support, not from just one person, but from several people. And she was open about it and vulnerable. And I think that was the most important thing. When her daughter was four months old, we made a real big plan. And not a just try it sometimes. We had concrete guidelines of how we wanted to go about it. And then she left the office and then we followed up again. And we said, okay, two weeks have gone by. Uh, here's our check-in. How's it gone? Have you tried it? No, I haven't tried it. Still really scared. Okay, let's do it. We're gonna make it this state and we're gonna have these structures in place. And she decided for her that that was gonna work best by doing it at her mom's house. And um, you know, she had support around her, she had a plan, and her daughter did great. Everything went fine. Second time, she didn't feel less scared. The anxiety actually hadn't gone away just because one successful occurrence, but she had to ground herself in the plan and she knew what she needed to do. And she did it even though she felt scared. And guess what? She came back to the phrase that we had talked about before. The risk of delaying is greater than the risk of knowing at this age. Finding out at four months with a plan and a medical team is a completely different story than finding out at a birthday party at age one or two. She had tools that her younger self didn't have. Her daughter did not have to repeat the same experience, even if she were to have had an allergy. Now, here's the twist. I haven't actually told you which baby was at higher risk. The answer will probably not be what you expect. Family history of food allergy, yes, it matters. But the baby whose mama had experienced anaphylaxis was at modestly elevated risk. I'm not dismissing that. But but it was only slight. And the biggest clinical factor between both of these kids was not family history and was not what their parents experienced. The thing that caught my attention and that tells me whose baby is at risk for this, it's our skin. And that is what I'm gonna dig into much deeper. Okay. So there's something called the dual allergen exposure hypothesis. And once you hear it, it'll make sense, I promise. But before I explain it, I want to give you a little history because understanding where we came from helps put into perspective why your mother-in-law, your mom, your neighbor, um, extended family, and maybe even your pediatrician might be telling you different things about when to introduce peanut butter. In the 1990s, the thinking was allergenic foods are dangerous, so delay them. And in 2000, the AAP officially recommended delaying peanut butter introduction until age three, eggs until age two. The logic seemed reasonable. If the immune system isn't ready, don't challenge it. Protect the baby by waiting. So an entire generation of parents and pediatricians did exactly that. They waited, they were careful, they followed the guidelines, and the caution around allergenic foods became baked into how we talk about feeding babies. And here's the problem peanut allergy prevalence tripled in the early 2000s. We were trying to protect babies, and anaphylaxis hospital admissions grew tremendously. And that made things worse. It caused people then to realize wait a minute, if avoidance isn't the strategy that's working, then what does? So in 2008, the AAP reverse course, they said, you know what, we actually don't have convincing evidence that tells us when to introduce allergenic food, but we know that delaying might not be right. So in 2015, the landscape completely changed. The LEAP trial, learning early about peanut allergy, took 640 high-risk babies and randomized them into two different groups. Okay. They took one group which took, which ate peanut butter regularly, starting between four and 11 months. And the other group totally avoided it just based on the guidelines that had previously been published. They followed both sets of these babies for years. But the results were impressive. In the group that introduced peanut early, peanut allergy rates dropped by 86%. 86%. You guys, that's impressive. Especially when they were not controlling these environments. And then the follow-up study confirmed that the protection lasted. This wasn't just tolerance while they were eating it. This was real immune learning. The rates of peanut allergy in the group that had later introduction was similar to the population data that was reflective of the recommendations at the time. So that said, this landmark trial was published in 2015, but there has still been what I would call an implementation gap. Not everybody has seen all the data, seen the translation of that, and not everybody knows how to introduce it. And so that's why your family members all have different things to say, because more than likely, depending on when they were raising a baby, they were given different recommendations. And it's done a full 180 in 25 years' time span. Not much time to have radically different recommendations. It's just that the messaging has genuinely been inconsistent. And this is really difficult. Now, the question becomes why? Why did that early allergen exposure make such a difference? This is where the dual allergen exposure hypothesis comes in. And this is the part that I think is fascinating. The idea is this there are two ways your immune system can encounter a food protein. One is through your belly, through eating. And when that happens in early infancy, in the right window, the immune system tends to say, okay, this food, we're good. Learns tolerance, learns that that peanut protein or egg protein belongs here. The other way is through our skin. When a food protein gets in through a disrupted barrier through eczema, like dry, cracked skin, the immune system can learn something very different because our skin is our biggest barrier and has a very active part in our immune system. And it can interpret that protein as an intruder. Think of it this way: your skin is like a brick wall, right? Like that top layer. And if that brick wall is broken and something gets underneath, our immune system should work and tell us, hey, something is invading. We need to know and create a response so that we can protect our skin. It's really smart. Our bodies are amazing. It's a threat. We need to mount a response accordingly. The problem is that it teaches and primes the same channel in the skin as in the gut if there's a food protein that shouldn't be there. And that can trigger an allergic response and one that creates memory. So the memory then holds on to that food protein saying, it is bad. Please don't invade again. This is why babies with eczema who aren't eating peanut yet can still become sensitized to it. This the peanut dust that's in the environment, like on surfaces, in the air, on your toddler's hands, is actually getting into the skin before it ever gets into the mouth. And the immune system is learning the wrong lesson first. So the skin isn't just a symptom that I like to manage. I'm pretty aggressive about treating eczema in my early babies because it's about food allergy risk too. The skin is a pathway and the condition for your baby's skin, specifically whether your baby has eczema and how significant that eczema is, is actually one of the strongest risk factors we have for food allergy development. And a brand new meta-analysis just published this year confirms that eczema in the first year of life is associated with roughly a four-fold increase in the odds of food allergy presentation, which means eczema severity increases food allergy risk incrementally. And this is specifically why I am so interested in early introduction for those allergenic exposures through the gut and through the mucosa, because it's important for our bodies to learn and become sensitized with getting the right message at the right time. So I am looking at skin from the beginning and having these conversations early. And it's why with the mama who had anaphylaxis, I was having these conversations from the newborn visit. We were talking about her baby's skin. And that was our first lens to prime and reassure that we were going to do everything we could to help mitigate this. One really cool thing that we know is that if we start taking care of and hydrating the skin, if we start doing that before we see it erupt, say in that realm of under nine weeks, I usually start by like three to four weeks, we can actually reduce our risk of eczema by 50%. Okay. Impressive. I actually like to prime the conversation with, let's start with actually skin management early on. And I say that three to nine week window because that's actually when we start seeing that emerge. Skin takes a full month to turn over. Your baby's skin in the first month of life is the skin they had in the womb. Their real skin doesn't really come out until a month of life. And so if we're starting to see their first layer of skin already dry, then our skin barrier is at higher risk for being sensitized. And if I can do anything to help that barrier stay strong and protected, that's going to help my baby longer term. But I want to make it really clear I am NOT saying that if you prevent eczema, you will prevent food allergies. I'm not, because that's been studied two, and unfortunately, it's more complicated than that. There's a pretty big trial called the Prevent At All trial, and they looked at regular use of skin emollients and whether it would reduce food allergy. And the answer: not really. Emolliants alone, like Vaseline, Cerev, moisturizers like this, they would not prevent the skin sensitization that's already happening. Manage the eczema well? Yes. But understand that it's not a guarantee that you've closed the window on food allergy risk. It's just a piece of a bigger picture. The other piece is still get the food in in the right window. So the timing of when we want to introduce allergens actually comes down to the severity of our eczema. A little bit is mild, okay? Like a little dry patch here and there responds to lotion. It's not all over the body from head to toe. And we hardly ever have to do a little bit of hydrocortisone. They respond pretty well as long as they stay moisturized. That's mild eczema. Moderate eczema is when you have these pretty big flares that get red and scaly or itchy, and you need to really control that with a steroid even pretty early on. And that moderate situation is the plan where we really want to hone in on and really make sure we're introducing peanut and egg at an earlier time. So four to six months for those babies. No testing is needed first with analogist. We just want to make sure we get good exposure early. Now, if your baby has severe eczema, I'm talking widespread, persistent, really flaring a lot, you're having to have multiple appointments with your doctor about their skin before they're six months of age. We probably are high risk and should have some testing first. So if you're lying awake thinking, my husband is allergic to tree nuts, so we have to do this in the air parking lot. I just want you to like take a breath. That's not the risk stratification that really matters. We don't need to do that. What really we need to do is think about how we can support the skin so that we can reduce the risk as much as we possibly can. Here's some myths that need to go. The things that I hear regularly that have no evidence behind them and in some cases have actual evidence against them. And I say this with love because I know you've heard these things from someone who loves you and who has maybe heard something a little bit backwards without the full context. But I'm giving you permission to let these things go. Okay. Myth number one: if you ate carefully during pregnancy or breastfeeding, say you had a lot of peanut butter because you wanted to make sure that your baby didn't get peanut allergy. This does not influence your baby's allergy risk. Okay. I need you to hear this clearly. No evidence that restricting or aggressively eating an allergenic thing during your pregnancy or while breastfeeding will prevent your food allergy. This has been well studied, but no evidence. Okay. Moving on. Myth two breastfeeding protects against food allergies. Breastfeeding does have a lot of real benefits, and I'm a huge fan of breastfeeding. Okay. But for food allergies specifically, the evidence does not support breastfeeding as completely protective. So I say this with love that if you've been breastfeeding and holding on to that thinking this is going to help them prevent their food allergy, there's not significant data for this. So if you formula fed your baby and your kid has an allergy, this is not a cause and effect story, again, let that go. No guilt. Myth number three: hypoallergenic or hydrolyzed formula is going to reduce their risk. This one matters a lot because there are some claims here. So in 2019, an AAP report actually reversed a previous position on this. The evidence does not support partially or extensively hydrolyzed formulas for preventing atopic disease like eczema or food allergies, even in high-risk patients. These formulas have their place and they really need to stay on the market for good reason. They're indicated in managing very specific things. But buying them prophylactically as prevention for eczema or for food allergies will not help. I'm very sorry. Now, that said, there is more nuance in this conversation for another. Day on calmic protein allergy, but this is not going to prevent the food allergies. Myth number four. I've already alluded to this, but waiting longer means lower risk. And I know the thought here because this is a generation-old story of telling people to delay peanut allergies. The very real thought, though, that goes through a lot of minds, especially the minds of my mamas who have allergy, is that they're afraid of their baby's airway and that they would say, gosh, I'm I would be so afraid that if they had a reaction, that it's going to happen so much faster or be so much more severe because they're so little. And to that, I like families to know that again, delay is not protection. The difference in your baby's airway from four months to six months is not significant. Even six months to 12 months, not enough for us to make a difference here. So in a follow-up study from the LEAT trial, in 2023, there was an analysis that showed that every month of delaying diminishes the protective effect of early introduction. So if you introduce allergens four to six months and you're at high risk, you're decreasing that risk by about 77%. Okay. If you wait until they're 12 months, you only get about a 33% reduction in that risk. Which means that I wasn't worried about the two or the three-week delay that my mama who'd had anaphylaxis was doing. I would be worried, and I did tell her at seven months you are at higher risk than at six months. So we really need to move forward. Okay. And every month that this goes on, you're increasing that risk. I'm not telling you all this to scare you. I'm telling you this because I want you to walk away today with something useful because the fear is real. The history is real. Your family's experience is real. And now we have tools that we didn't have 20 years ago. We can have a plan with evidence. Here's myth number five: probiotics and supplements. This one is also nuanced. Okay. And part of this is because discerning which strain and which baby is like a needle in a haystack, kind of. But a really big 2025 Cochrane review found that probiotic supplementation may have little to no effect on food allergy incidents in infancy. Prebiotics, same story. Supplements are not without potential benefit in other areas. And so I do think that there's a role for them. But the evidence for food allergy prevention is not necessarily there yet. So that said, I want to just make it clear because a lot of formula companies are actually looking at this, looking at very specific probiotic strains and very specific prebiotic strains to see which ones can potentially reduce risk of food allergies. And actually, there is some emerging evidence, but it again, it is strain specific, and we don't know enough yet to make broad terms. I will say the strains that they are looking at happen to be things that naturally happen in breast milk. So the problem here is that when you have a control that's breast milk, it's really hard to see the difference in this. So I think there's more to this story. And I don't say don't use probiotics or don't use prebiotics. I'm just simply saying that I don't have enough information to give you clarity beyond what we know now. So here's where I want to land today. If your baby has no eczema, no food allergy history, you can start introducing allergenic foods around six months alongside other complimentary foods according to the AAP at home, no testing needed, peanut butter down. You can thin it down with water, breast milk, using two teaspoons. I personally recommend with my families to take a little bit on your fingertip and rub it on the inside of the cheek. As long as it's getting inside the oral mucosa, it doesn't necessarily have to be swallowed all the way down to the gut, although in the studies they were trying to achieve that. So they gave them larger volumes to do so. At this stage, though, your baby's tongue extrusion reflex is still present. And so they tend to push things out of their mouth, which means that it gets on their face. So personally, in my clinic, I actually say, why not? Let's do it four to six months. Because what happens here is that when a baby is able to hold their head up, I will proceed. They don't have to have all the other signs of readiness for me to do these two different exposures. But I do like to counsel them on early exposure because what it does for me is it helps that family have the scariest part of food introduction done first before we even get to the six-month visit. And that primes us for having a much richer and more robust conversation, the six-month visit, instead of cramming it all in at once, because there's a more important texture exposure that we need to get to at the following visits. So this is about building a skill, not just checking a box. The parents are building the skill in terms of trusting a baby and learning exposures too. Okay. So you have your baby, you're going to introduce this, you put some peanut butter in their mouth, and you see how it goes. I recommend doing this in the morning to midday so you can watch and see. Most families who have allergy will actually see nothing at all the first time, which is why we recommend doing it multiple times. If anything's going to happen, it's going to be within 20 minutes. You would see hives on the face, and you would probably see that spread with a subsequent exposure. If you're going to have a reaction, it may take up to an hour to four hours even if you're going to see a very subtle response. But it won't just be on the face. It'll typically be hives that go all over. You might also see vomiting or diarrhea. If those things happen, take pictures, call your pediatrician, and they'll walk you through what to do. A lot of the time, this resolves on its own without any intervention at all. Or if you need something, it ends up being anahistamine like children's or tech, and then you're resolved. Very rarely do these experiences land kids in the ER, even in our higher risk babies. And the reason is because while their immune system is sensitized, it's not yet so sensitized. They have these really dramatic effects. And that's why we want to know, because we want to know in a controlled environment so that we have the tools in case they have accidental exposure. Now, for egg, I typically do soft scrambled egg and I tend to do the same kind of thing on a different day than peanut and I'll rub it inside the cheek. They don't necessarily have to swallow it for it to achieve the goal. We just want to get it in their mouth. If your baby has mild to moderate eczema, same plan. Okay. We want to introduce early, at home as safe, get a plan with your pediatrician. But the biggest importance is that you guys have already worked on taking care of your skin. If your baby has severe eczema, say it's widespread all over, hard to control, you've gone through multiple rounds of steroid creams and we haven't seen improvement, or we get big flares that just take a long time to get over. These are the babies that we should consider testing first. And this is where an allergist can get involved, and they can actually do skin print testing on your baby to see if the skin has already mounted a response to these allergens. And then that will guide them on when they're going to do exposure. And then often those babies will do a oral challenge in the allergist's office to demonstrate how severe that response is. So if you have a personal food allergy history, let your pediatrician know. Ask about risk stratification based on your baby's skin. Family history alone generally puts baby at a low to moderate risk category. But the skin picture really, really matters. And if you're anxious and if this topic makes your heart rate go up and even putting this off because you feel like it's just too scary or you can't do it alone. I want you to know that what that mama did in my office who was successful and who has a baby who is not allergic to anything, this can be you two. Okay? Get the support you need, manage your anxiety, and move forward. Be brave and know that this makes a difference. Because at the end of the day, preventing these food allergies to the best of our ability is something that we have a little bit of play in. It's not completely up to us, but the this can make a big difference. You don't have to feel calm to take the next step. You just need a plan. Because here's the thing I want to leave you with today. Your fear makes complete sense. And I have never met a person with a food allergy who doesn't carry real anxiety about it. It's not irrational, it's not dramatic. Fear does get a voice in the room, but it doesn't get the final vote. You get to have the tools and take advantage of the window. And the worst thing you can do is let that fear slow you down from making a plan. Thank you so much for being here today. If this episode has helped you, share it with a new parent, a friend, maybe your pediatrician even, because there is an implementation gap. I see this even in my own community here. And the process of being able to implement this early allergenic exposure can make big impacts down the road for our kids. And so I want this information everywhere. Okay. Share it with your mom group. Share it anywhere you can because it doesn't need to be stuck in a guideline. It needs to be in the hands of the moms who want to take action like you. If you want to go deeper on infant feeding in that zero to four month window, I actually just wrote a course about this. It's called Read the Pattern. You can go to Newstorynutrition.com and get the link for that. I put my heart and soul into that course because it's the conversation I wish I could have with every new parent before they leave the hospital and at all of my checkups in between. I walk you through what to know, how to support your baby, how to interpret patterns without worrying about every detail in the process. And then grow your skills so that you can read your baby and trust yourself in the meantime. See you guys next week.