Introducing Allergens to Your Baby: The Safe Way, and Why Waiting Backfires

If you were pregnant a decade ago, or if your mother is advising you, you may have absorbed a rule that said avoid peanuts, wait on egg, delay the risky foods as long as possible. That advice was withdrawn, and the evidence now points firmly the other way.

This is one of the few areas of infant feeding where getting the timing right genuinely changes outcomes, so it is worth understanding rather than just following.

What Changed, and Why

The old logic seemed sensible: if a food might cause a reaction, keep it away until the immune system matures. Guidance across several countries recommended exactly that.

Then the data came in, and it showed the opposite. Rates of peanut allergy rose in countries that recommended avoidance, and were markedly lower in populations where peanut is introduced early and eaten regularly. Trial evidence, most prominently the LEAP study on peanut introduction, found that early introduction substantially reduced the likelihood of developing an allergy compared with avoidance.

The mechanism appears to be that the infant gut learns tolerance through exposure. Delay it, and the first meaningful encounter can happen through the skin instead, particularly in babies with eczema, which is more likely to prime a reaction than build tolerance.

So current NHS guidance is to introduce allergenic foods from around six months, alongside other first foods, and not to delay.

The Main Allergens to Introduce

These are the ones responsible for the large majority of food allergies. All of them should go in during weaning.

• Cow's milk, in food such as yogurt, cheese or milk mixed into cereal. Not as a main drink until twelve months.
• Egg, well cooked to begin with. Scrambled, hard boiled, or baked into something.
• Peanut, as smooth peanut butter thinned with milk or water, or fine peanut powder. Never whole nuts, which are a choking hazard until around five.
• Tree nuts, the same way: smooth nut butters or ground.
• Fish, well cooked and carefully boned.
• Shellfish, well cooked.
• Soya, as tofu or soya yogurt.
• Wheat and gluten, as bread, pasta or cereal.
• Sesame, as smooth tahini or hummus.

How to Do It Safely

The method matters as much as the timing, and it is straightforward.

One at a time. Introduce a single new allergen and wait a couple of days before the next. If something does happen, you need to know which food caused it.

Start small. A quarter teaspoon on the first go is plenty. If that is fine, increase gradually over the following days.

At home, and earlier in the day. Not at nursery, not at a restaurant, not right before bed. You want to be present and awake for the hours afterwards.

Not when they are unwell. A baby with a cold or a rash makes it much harder to interpret what you are seeing.

Then keep it in the diet. This is the part most often missed. Tolerance is maintained by regular exposure, so once a food is in, offer it about once a week or more. A baby who ate peanut butter twice at seven months and never again has not really been introduced to it.

What a Reaction Looks Like

Most reactions are mild and appear quickly, usually within minutes to two hours.

Mild to moderate signs: raised red hives or a rash, particularly around the mouth or where food touched skin, swelling of the lips, face or eyes, itching, vomiting, diarrhoea, or a runny nose and sneezing. If you see these, stop the food, and speak to your GP before offering it again.

Signs of anaphylaxis, which is a medical emergency: difficulty breathing, noisy or wheezy breathing, a swollen tongue or throat, difficulty swallowing or speaking, sudden floppiness or unresponsiveness, or pale and clammy skin.

If you see any of those, call 999 immediately. Do not wait to see whether it settles, and do not drive to hospital yourself if you can call an ambulance instead.

Worth knowing: a red rash around the mouth from acidic foods like tomato, strawberry or citrus is extremely common and usually irritation rather than allergy. It appears only where the food touched, and settles quickly. If you are unsure, it is always worth asking rather than guessing.

Practical Ways In

Getting nine allergens into a baby who eats a teaspoon at a time sounds harder than it is.

• Peanut: smooth peanut butter thinned with your baby's usual milk into a loose paste, stirred through porridge or spread thinly on a soft finger of toast.
• Egg: a well-cooked scrambled egg finger, or hard boiled and mashed with a little yogurt.
• Sesame: hummus, which also delivers iron, or a smear of tahini in porridge.
• Fish: flaked cooked salmon mashed into potato, checked very carefully for bones.
• Dairy: full fat plain yogurt, which is usually an easy win.
• Wheat: a strip of toast or well-cooked pasta.

Once introduced, a rotating weekly pattern keeps everything in the diet without much thought: peanut butter on toast two mornings, hummus with lunch twice, yogurt daily, fish once or twice a week, egg a couple of times.

If you have not started solids yet, our guide to when and how to begin weaning covers readiness signs and the first two weeks.

Common Worries, Answered

Keeping Track Without Making It a Project

Nine allergens, introduced one at a time, then maintained weekly, is genuinely more than most people can hold in their head during a period of broken sleep. A simple record helps more than it sounds: what was introduced, when, whether anything happened, and when it was last offered.

That last column is the one people miss. It is easy to introduce everything conscientiously in month one and then realise in month four that your baby has not had fish since. A note on the fridge works perfectly well; so does the allergen tracker in our app. The tool matters far less than having any record at all.