Introducing Allergens to a Baby

Early rather than late, one new food at a time with a day between, in forms a baby can safely swallow — and then kept in her diet rather than offered once and dropped. That is what the AAP and the NHS both now describe, and it is close to the reverse of what parents were told a decade ago. If there is eczema, an existing allergy, or a family history of allergy, eczema, asthma or hay fever, the first step is a conversation with your GP, health visitor or pediatrician before the first taste — not after it.

This page describes published guidance and says who to ask. It names no condition in your baby, suggests no test, no elimination and no amount, and it cannot do the one thing that matters here, which is look at her.

Who asks somebody first

Put this before the method, because for some families it changes the method.

The AAP is explicit: a baby with severe persistent eczema, or one who has had an immediate reaction to any food, is considered at high risk for peanut allergy, and her pediatrician should be asked first. The NHS says the same from its side — families with an existing allergy, eczema or a family history should talk to a GP or health visitor before starting.

"First" means before the first taste of the food in question, not after something goes wrong. If you are reading this and wondering whether the history in your family counts, that wondering is itself the reason to ask.

The advice reversed, and this is the sentence

For years the instruction was to hold the risky foods back, sometimes for years. Newer work went looking for the benefit in that and did not find it. The AAP's position now is that there is no evidence that delaying baby-safe soft forms of egg, dairy, soy, peanut products or fish beyond 4 to 6 months of age prevents food allergy. The NHS goes a step further in the other direction: delaying peanut and hen's eggs beyond 6 to 12 months may increase the risk of developing an allergy to them.

So the idea that delaying allergens prevents an allergy is not merely unsupported here — it is the thing that was tested and failed. What replaced it is not a guarantee in the opposite direction. No source on this page says early introduction protects any particular child; they say the delay has no benefit and may cost something.

The two bodies phrase the timing differently, and you should see both. The AAP describes starting once a baby is ready for solids and ideally offering peanut-containing products as early as 4 to 6 months. The NHS frames the whole of weaning as beginning at around 6 months. The readiness signs are what both are really pointing at.

The trial underneath the guidance

The evidence people mean when they cite this is LEAP. It randomised 640 infants who already had severe eczema, egg allergy or both — at least 4 months old and under 11 months at the start — to eat peanut or avoid it until 60 months of age.

Among those whose skin-prick test was negative at the start, peanut allergy at 60 months was 13.7% in the avoidance group against 1.9% in the group who ate it. Among those whose test was positive at the start, it was 35.3% against 10.6%. There was no significant difference between the groups in serious adverse events. The authors concluded that early introduction of peanut significantly decreased the development of peanut allergy among children at high risk of it.

What that trial was not is as important as what it was. It was not a study of babies at ordinary risk — every infant in it already had severe eczema, egg allergy or both. It was not families deciding at home: it was a supervised trial that screened its participants first, and describing that screening here is not a suggestion that anybody should go and seek a test. And it is not a promise about an individual child. A difference between two groups over five years tells you which way the odds moved; it tells you nothing about what will happen at your kitchen table.

The method, as it is published

Start solids with a few low-risk foods. Give one new food at a time and wait at least a day before the next, watching for diarrhoea, rash or vomiting. Then bring in the more allergenic ones, still one at a time — egg, nut products, yogurt or other dairy, wheat, sesame, soy, fish and shellfish.

The NHS's fuller list of foods that can trigger a reaction: eggs; nuts and peanuts, finely ground or as nut butters; cows' milk; foods containing gluten; beans, lentils and peas; seeds; soya; shellfish; fish; celery; mustard; and sulphur dioxide.

Once one of them has been introduced and she has taken it without trouble, it becomes part of her usual diet rather than a box ticked. That is the part most often missed: the guidance is about keeping these foods in the routine, not about a single successful spoonful.

Form matters more than anything else on this page. Never give whole peanuts or tree nuts to a baby or a young child — they are choking hazards that can block the airway, and an inhaled one can cause a severe and possibly fatal chemical pneumonia. The AAP puts whole peanuts off the table until a child can chew them well, usually at least 4 years; the NHS says under 5 for whole nuts of any kind. Take the more cautious of the two. Peanut instead goes in thinned: stirred into cereal, puréed fruit or yogurt, or dissolved in breast milk or formula and given on a spoon. Solids by age carries the rest of the food-safety rules, and they all apply here too.

Amounts: the AAP's examples, and the limit of them

The AAP does give example portions, and they are smaller than most people expect: about 2 teaspoons of peanut butter, or of a nut butter such as cashew or sesame tahini, and about a third of a well-cooked egg. It calls them developmentally appropriate portions rather than doses, and the point of them is regularity — a small amount kept in the routine — rather than a quantity to reach.

What no source here gives is a schedule of how often, a gram figure, or an amount for any other food on the list. Those are the exact instructions that should come from somebody who knows her history, and if any of the ask-first paragraph above applies to you, the portions above are a conversation with your pediatrician rather than a green light. This page cannot see your baby.

What a mild reaction looks like, and when

Most reactions are mild. The NHS describes swollen lips or face, itchy watery eyes, wheezing and coughing, an itchy rash, worsening eczema, vomiting, tummy pain, diarrhoea or constipation.

Timing varies with the food. Reactions usually happen within minutes, but can take up to 2 hours — and up to 3 days in the case of cows' milk. That range is why one new food at a time with a clear day between is the method: it is the only way anything that appears has something to point at. Writing down what went in and when — on the feeding chart or the day log — beats reconstructing a week afterwards, and it is the record a clinician can read.

Anything mild, repeated or unclear is a GP or health visitor appointment. Anything in the emergency box above is a phone call to an ambulance, first, before anything else.

The one thing not to do on your own

Do not cut a major food out of her diet without advice. The NHS is direct about why: a child can lose the nutrients that food was providing, and milk, egg and wheat are not small parts of a diet at this age. An allergy a GP has confirmed comes with a plan for what replaces the food; an allergy guessed at over a nappy change comes with nothing.

The same goes in reverse. If a food has already caused an immediate reaction, do not test it again at home to see what happens. That is a clinic's job, and only a clinic's.

When the meals start settling into a shape, the feeding schedule for 6 to 12 months covers how milk and solids share the day through this year.

This page is general information, not medical advice. It describes what the AAP, the NHS and one randomised trial have published, and nothing more: this page cannot see your baby, and it is not a substitute for the person who can examine her.