Introducing Allergens to Your Baby: Peanut, Egg, and More

Why the advice changed

For years, parents were told to hold off on peanuts, eggs, and other allergenic foods until toddlerhood. That guidance has been reversed. National guidance shifted with the NIAID’s 2017 addendum guidelines on early peanut introduction, followed by the American Academy of Pediatrics’ 2019 clinical report on allergy prevention — both reflecting newer research showing that delaying these foods doesn’t protect against allergy, and may actually raise the risk. For most babies, high-allergen foods can be introduced as soon as solids are started, generally somewhere around 4 to 6 months of age.

The turning point was a landmark 2015 study (known as the LEAP trial, published in the New England Journal of Medicine) that followed infants at high risk for peanut allergy. Babies who ate peanut products regularly and early developed peanut allergy significantly less often than babies who avoided peanut. That single trial reshaped guidance across pediatrics, and the AAP now recommends introducing peanut and other top allergens around the same time solids begin, typically 6 months.

Food allergies aren’t rare. Roughly 7.6-8% of children in the U.S. have one, and close to 40% of allergic children are allergic to more than one food. Nine foods account for about 90% of those allergies: milk, eggs, wheat, soy, peanuts, tree nuts, fish, shellfish, and sesame. Sesame is the newest addition to that list — it’s been a required label disclosure on U.S. packaged foods only since January 2023. Among children specifically, milk, peanut, and shellfish tend to be the most common.

The general approach

A few simple habits make allergen introduction calmer and safer, regardless of which food you’re starting with:

• Introduce one new top allergen at a time. Give it a few days before adding the next one, so if a reaction shows up, you know exactly what caused it.
• Offer it earlier in the day, not right before a nap or bedtime, so you’re awake and able to watch for a reaction rather than discovering one hours later.
• Pair it with a food your baby already tolerates well. That way, if something seems off, you can be confident it’s the new food and not the familiar one.
• Skip it if your baby is sick. Cold or stomach-bug symptoms can look similar to allergy symptoms and muddy the picture.
• Start small. A taste or two is enough for a first try — you’re not trying to fill your baby up, you’re watching how their body responds.

If your baby has eczema, or if food allergies run in your family, it’s worth talking with your pediatrician before you begin. Some higher-risk babies benefit from a more structured or supervised introduction plan, and your pediatrician can help you decide what makes sense.

A note on breastfeeding and pregnancy

There’s no evidence that a parent needs to avoid peanuts, eggs, or other top allergens during pregnancy or while breastfeeding to protect their baby from developing allergies — restriction hasn’t been shown to help. Breastfeeding for the first few months is linked to a lower risk of eczema in the first two years of life, and longer breastfeeding may be associated with lower asthma risk in early childhood; both eczema and asthma are, in turn, linked to higher food-allergy risk. The evidence on breastfeeding directly preventing food allergy itself, though, is inconclusive.

The nine foods, one at a time

Here’s a practical rundown of each major allergen and an easy way to offer it for the first time.

• Milk. A milk allergy is a reaction to a protein in cow’s milk — it’s a different thing from lactose intolerance, which doesn’t involve the immune system. Cow’s milk shouldn’t be given as a drink before 12 months, but yogurt and cheese can be introduced earlier as foods.
• Egg. Common in young children and frequently outgrown. Serve well-cooked — scrambled or hard-boiled are easy starting points. Some children who react to raw or lightly cooked egg can still tolerate egg baked into things like cake.
• Wheat. A wheat allergy is separate from celiac disease or a gluten sensitivity. Toast or soft, well-cooked pasta are simple first foods.
• Soy. Found in soybeans and soy foods like tofu, and often hidden in packaged foods, so labels are worth checking once your baby is eating more broadly. Soft tofu is an easy way to introduce it.
• Sesame. Try hummus made with tahini, spread thinly on toast.
• Fish (salmon, cod, tilapia, and similar). A separate allergy category from shellfish. Fish can be introduced around the time solids start — forming it into a small patty makes it easier for a baby to manage.
• Shellfish (shrimp, crab, lobster, mussels). Distinct from fish allergy, and reported to be more common in adults than young children. Once your baby is eating finger foods, shellfish can be served pureed or cut into small, manageable pieces.
• Tree nuts (almond, cashew, walnut, pecan, hazelnut, pistachio). Whole nuts are a choking hazard at any age this young — never serve them whole. Instead, spread nut butter very thinly on toast or stir a small amount into oatmeal or yogurt.
• Peanut. One of the most common childhood allergies, and the one with the strongest evidence behind early introduction. As with tree nuts, whole peanuts and peanut pieces are a choking hazard — safe forms are peanut butter thinned and spread thin, or peanut butter puffs.

If your family doesn’t already eat certain foods on this list — shellfish or tree nuts, for instance — there’s no requirement to introduce them early just for allergy-prevention purposes. The strongest evidence for early, deliberate introduction is specifically around peanut.

Introducing peanut butter, step by step

Because peanut allergy is common and the evidence for early introduction is so well established, it’s worth walking through peanut specifically.

Before the first taste, especially for a baby at higher risk (significant eczema, a diagnosed egg allergy, or a strong family history), check in with your pediatrician — some babies benefit from an in-office first taste or an allergy evaluation first. When you do start, pick a simple, sugar-free peanut butter with minimal added ingredients, and offer just a small amount.

Because whole peanuts and peanut pieces are a choking hazard for children under about 4 years old, peanut butter always needs to be prepared in a safe form:

• Spread thinly on toast and cut into thin strips
• Thinned with breast milk, formula, water, or a puree your baby already eats (baby cereal, mashed banana, applesauce) for spoon-feeding or baby-led weaning
• Offered as peanut butter puffs, which are designed to dissolve easily

A rough guide by age:

Age	What’s appropriate
6–9 months	Small amounts of peanut butter or peanut-containing purees; no whole peanuts
9–12 months	Continue small peanut servings; peanut butter puffs work well for self-feeding
12 months+	Peanut in mixed foods, like a thin peanut butter sandwich or a peanut-containing muffin

Whole peanuts, peanut chunks, and other hard, round, or sticky foods that size stay off the menu until roughly age 4, regardless of allergy status — this is a choking-safety rule, separate from allergy timing.

Beyond allergy prevention, peanuts bring real nutritional value to a growing baby’s diet: plant-based protein, energy-dense fats, fiber, and nutrients like folate, magnesium, vitamin E, and B vitamins.

What to watch for

Reactions to a newly introduced allergen vary — a baby can react differently on different exposures, and severity isn’t always predictable in advance. Watch for:

• Hives or an itchy rash, including a flare of eczema
• Swelling, especially of the lips, face, or eyes
• Sneezing, coughing, or wheezing
• Throat tightness or a change in voice/cry
• Vomiting or diarrhea
• Pale or flushed skin, unusual sleepiness, or light-headedness

Most reactions show up within minutes to two hours of eating; in rare cases, onset can take four to six hours or longer. If you notice any of these signs after a new food, stop offering that food right away.

When to reach out

• Any hives, rash, or swelling that appears after a new food — pause the food and call your pediatrician to talk through next steps.
• Vomiting, diarrhea, or unusual fussiness that follows a new food closely enough to seem connected.
• Call 911 immediately for trouble breathing, wheezing, throat or tongue swelling, repeated vomiting, sudden paleness or limpness, or any combination of symptoms across the skin, breathing, and gut at once — these can signal anaphylaxis, a severe, fast-moving allergic reaction that needs emergency treatment.
• After any reaction, jot down what symptoms appeared, how long it took to start, and how long it lasted — that detail is genuinely useful for your pediatrician in sorting out what happened and what to do differently.

Allergy, intolerance, or something else?

These terms get used interchangeably, but they describe different things:

• A food allergy is an immune-system reaction to a food protein. It can be confirmed with medical testing and, because reactions are unpredictable, the main treatment is strict avoidance of the trigger food. A pediatrician or allergist may prescribe an epinephrine auto-injector for babies at risk of a severe reaction.
• A food intolerance — lactose intolerance is the classic example, along with sensitivity to certain additives — doesn’t involve the immune system, tends to be harder to pin down definitively, and often allows small amounts of the food without a problem.
• Celiac disease is neither an allergy nor an intolerance — it’s an autoimmune condition that requires strict, lifelong avoidance of gluten.

Allergies tend to run in families, and babies with eczema, asthma, or hay fever have a higher baseline risk of developing a food allergy.

If a food allergy is suspected, a pediatrician or allergist has a few ways to check: a skin-prick test (a small amount of the allergen is placed on the skin and lightly pricked — a raised bump suggests a reaction), a blood test measuring allergen-specific antibodies (less precise than skin testing), and an oral food challenge, where small, increasing amounts of the suspected food are given under direct medical supervision. The food challenge is the most accurate method, but it carries real risk of a significant reaction and should never be attempted at home.

The long view

Many food allergies fade with time. Most milk, egg, wheat, and soy allergies are eventually outgrown, but resolution is gradual and often isn’t complete until later childhood or adolescence rather than by age 5. Peanut, tree nut, and shellfish/fish allergies are less likely to resolve and more often carry into adulthood. If your baby is diagnosed with a food allergy, working with your pediatrician (and often a registered dietitian) on label-reading and safe substitutions can help you avoid the trigger food while still covering your baby’s nutritional needs as they grow.

Introducing allergens can feel like a high-stakes moment the first time you do it, but for the vast majority of babies it’s a routine part of starting solids — go one food at a time, watch for a couple of hours, and keep building your baby’s diet outward from there.

Sources

Written from primary pediatric sources. This is general information, reviewed editorially rather than by a clinician — it isn’t a substitute for your pediatrician’s advice about your child.

• American Academy of Pediatrics (HealthyChildren.org) — When to Introduce Egg, Peanut Butter & Other Common Food Allergens to Your Baby
• American Academy of Pediatrics (HealthyChildren.org) — AAP Clinical Report Highlights Early Introduction of Peanut-based Foods to Prevent Allergies
• New England Journal of Medicine — Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy
• Cleveland Clinic — The Most Common Food Allergies
• Mayo Clinic — Food allergy — Symptoms & causes
• Mayo Clinic — Anaphylaxis — Symptoms & causes / First aid
• NIH / National Institute of Allergy and Infectious Diseases (NIAID) — Diagnosing Food Allergy
• American Academy of Pediatrics / Pediatrics journal — The Public Health Impact of Parent-Reported Childhood Food Allergies in the United States