How to Introduce Allergens to Baby: A Step-by-Step Guide

The advice most of us grew up with, delay peanuts and eggs until your child is older, turned out to be wrong, and the guidelines now say the opposite.

Introducing allergens is the part of starting solids that makes parents most nervous, and for understandable reasons. It is also one of the few areas of infant feeding where following current guidance appears to meaningfully reduce the chance of a lifelong food allergy.

This guide covers why early introduction is now recommended, when to start, baby-safe forms of all nine major allergens with a practical table, a step-by-step method for a single introduction, exactly what an allergic reaction looks like and what to do, and the myths that still cause unnecessary delay.

Why Early Allergen Introduction Is Now Recommended

For years, parents were told to delay peanuts, eggs, and other common allergens until age one, two, or even three. That advice was withdrawn because the research went the other way. Delaying introduction did not prevent food allergies, and the evidence now suggests it may have contributed to the rise in them.

The turning point was the LEAP trial, published in 2015, which randomized infants at high risk of peanut allergy to either eat peanut regularly from between four and eleven months, or avoid it entirely until age five. The early-introduction group had a dramatically lower rate of peanut allergy at five years. The follow-up EAT study extended similar findings to other allergens.

As a result, national guidelines now recommend introducing common allergens early, generally around the time solids start, and keeping them in the diet regularly rather than offering them once and moving on. The regularity part is the piece most parents miss.

When to Start

Start allergens once your baby is ready for solids, which for most babies is around six months and not before four. The developmental signs matter more than the birthday: sitting with good head and trunk control, losing the tongue-thrust reflex that pushes food out, showing interest in food, and being able to move food to the back of the mouth and swallow.

In practice, a sensible sequence is to begin solids with a few simple foods for several days, confirm your baby is handling the mechanics of eating, and then start working allergens in. There is no benefit to waiting longer, and guidelines are explicit that delaying past twelve months is not protective.

Talk to your pediatrician before starting allergens at home if your baby: has moderate to severe eczema, particularly eczema that needs prescription treatment; has an existing diagnosed food allergy; or has had a previous reaction to a food. Babies with severe eczema are the group for whom guidelines suggest earlier peanut introduction, often around four to six months, sometimes after allergy testing or in a supervised setting. That is a conversation to have rather than a decision to make alone.

The Major Food Allergens and How to Serve Them Safely

US labeling law recognizes nine major food allergens, which account for the large majority of food allergic reactions. Whole nuts, spoonfuls of nut butter, and chunks of hard food are choking hazards for babies, so the form matters as much as the food.

Never give a baby or toddler whole nuts, whole grapes, popcorn, or a thick blob of nut butter straight from the spoon. Nut butter needs to be thinned to a smooth, easily swallowed consistency, and it is worth being deliberate about this because thick nut butter is a genuine choking hazard that gets overlooked in the rush to introduce peanut early.

How to Introduce an Allergen, Step by Step

• Pick a calm, well day. Not when your baby is unwell, teething badly, or overtired, because it makes any reaction harder to interpret.
• Go in the morning or early afternoon. That gives you the whole day to watch, and keeps you out of a 2am judgement call.
• Be at home, not at daycare or a restaurant.
• Offer a tiny amount first. A quarter teaspoon, mixed into a food your baby already accepts. Wait ten minutes and watch.
• If nothing happens, offer a little more. Build up to about a teaspoon or two across the sitting.
• Watch for two hours afterwards. Most significant reactions appear within minutes to two hours.
• Introduce one new allergen at a time, with two to three days between new ones, so you can attribute any reaction.
• Keep it in the diet. Once tolerated, offer that allergen at least twice a week in a regular amount. Occasional exposure does not maintain tolerance, and this is the step most often skipped.

You do not have to introduce all nine in a particular order, and you do not need to buy a commercial allergen introduction kit, though some parents find the pre-measured convenience worth the cost. Ordinary kitchen foods work perfectly well.

Signs of an Allergic Reaction and What to Do

Most reactions in babies are mild, and most babies who try allergens have no reaction at all. Knowing what to look for is still essential before you start.

Mild reaction signs: a few hives or red welts, redness or swelling around the mouth or face, mild itching, vomiting once, loose stool, or a flare of eczema. If you see these and nothing more, stop the food, take a photo, and call your pediatrician the same day for advice on what to do next. An antihistamine may be recommended, but ask rather than assume.

Signs of a severe reaction, anaphylaxis. Call emergency services immediately:

• Difficulty breathing, wheezing, noisy breathing, or persistent coughing
• Swelling of the lips, tongue, or throat, or a hoarse cry
• Widespread hives combined with vomiting or any breathing symptom
• Repeated vomiting shortly after eating a new food
• Pale, floppy, or unresponsive, or sudden unusual sleepiness
• Blue or grey coloring around the lips or face

Call emergency services rather than driving. If your baby has previously been prescribed epinephrine, use it and then call. Symptoms involving two body systems at once, for example skin plus breathing, or skin plus vomiting, should be treated as anaphylaxis until proven otherwise.

One condition worth knowing about because it looks different: FPIES, a non-IgE food reaction, causes profuse repetitive vomiting and lethargy typically two to four hours after eating, without hives. It needs medical care too, and it is often missed because it does not follow the classic allergy pattern.

Common Myths Worth Discarding

• Myth: delay allergens to be safe. Delaying does not prevent allergy and may increase risk. Current guidance is early and regular.
• Myth: avoid allergens while breastfeeding. Routine maternal avoidance during pregnancy or breastfeeding is not recommended to prevent allergy.
• Myth: a family history means you should wait. A family history is a reason to talk to your pediatrician and possibly introduce earlier, not later.
• Myth: eczema means food allergy. Eczema is a risk factor, not a diagnosis. Most babies with eczema tolerate allergens fine.
• Myth: one taste is enough. Tolerance is maintained by regular ongoing exposure, ideally at least twice a week.
• Myth: skin testing before every food. Routine allergy testing before introducing foods in low-risk babies is not recommended and produces false positives that lead to unnecessary avoidance.

If you are just beginning solids, our guides to starting solids and baby-led weaning cover the mechanics, and we have dedicated walkthroughs for introducing peanut butter and introducing eggs.

What an Allergist Would Add

The single most common mistake allergists see is not the introduction itself but what happens afterwards. Families successfully introduce peanut at six months, tick it off, and then do not serve it again for three months. Tolerance is not a one-time achievement; it is maintained by ongoing regular exposure. Twice a week is the usual benchmark, and building it into a routine food, peanut butter in the morning oatmeal, yogurt at lunch, is the way it actually happens.

The second is unnecessary avoidance based on a suspected reaction that was never confirmed. A single episode of vomiting or a rash after a meal is often coincidental, and removing a major food group from a baby’s diet on that basis has real nutritional and social costs. Reactions should be discussed with a clinician, not acted on permanently by guesswork.

And for families with a genuinely high-risk baby, severe eczema or an existing food allergy, the message is not avoidance. It is supervision. Early introduction is still the goal; it is the setting that changes.

Frequently Asked Questions