The rules around when to give babies peanut, egg, and other allergens flipped about a decade ago, and a lot of parents are still working from the old playbook — or no playbook at all. The old advice was to wait. The current evidence says the opposite: get those foods in early, around six months, alongside everything else.
This piece walks through what the trials actually showed, who the standard advice applies to, how to do the introduction practically, and what reactions to watch for.
Healthbooq is handy during this phase for logging which allergen you tried on which day and whether you noticed anything — a real record that beats trying to remember at the next health visit.
Why the Advice Changed: the LEAP Trial
The headline study is LEAP — Learning Early About Peanut Allergy — published in the New England Journal of Medicine in 2015. Researchers took 640 high-risk babies (severe eczema or egg allergy) and randomised them to either eat peanut regularly from 4–11 months or avoid it entirely until age 5. By age 5, peanut allergy was 13.7% in the avoidance group and 1.9% in the consumption group. That is roughly an 80% reduction.
The follow-up LEAP-On trial showed the protection held even after a 12-month break from peanut. The EAT study (Enquiring About Tolerance) extended the finding to other allergens — egg, milk, sesame, fish, wheat — in the general infant population.
The mechanism is straightforward: the immune system tends to develop tolerance to foods it meets early and often through the gut. Skin exposure (think eczema and peanut dust on a parent's hands) without oral exposure pushes the immune system the other way, towards sensitisation. The decades of "wait until two or three" advice almost certainly contributed to the rise in food allergy.
What to Introduce, and When
For a baby without significant eczema and no known food allergy, start allergens from around six months alongside everything else you are offering. The list to get through:
- Cow's milk products — yoghurt, cheese, milk in cooking. Whole cow's milk as a main drink waits until 12 months.
- Cooked egg — well-cooked, no runny yolk. Scrambled, hard-boiled, or baked into something works fine.
- Peanut — smooth peanut butter thinned with warm water, expressed milk, or formula and stirred into porridge or yoghurt. Whole peanuts and chunks of nut butter are choking hazards until age 5.
- Tree nuts — same rules as peanut. Smooth almond or cashew butter thinned out.
- Wheat — toast fingers, pasta, cereal.
- Fish — flaked white fish or salmon, bones carefully removed.
- Sesame — tahini stirred into food.
- Soy — tofu, soy yoghurt.
Introduce one new allergen at a time and wait two to three days before the next, so you can pin down what caused any reaction. Pick a day when your baby is well — not mid-cold, not raging through teething pain. Do it in the morning or at lunchtime, when you can watch them for the next couple of hours and the GP surgery is open if you need it. The first taste does not need to be a feast. Even a quarter-teaspoon of peanut butter mixed into porridge counts.
Once a food has been tolerated, keep it in the diet regularly — at least once a week — to maintain tolerance. Stopping for months can let sensitisation rebuild.
What a Reaction Looks Like
Most reactions are mild and look like this: red blotches or hives around the mouth where the food touched, a bit of lip swelling, watery eyes, maybe a runny nose. They start within minutes to an hour and fade in one to two hours. An age-appropriate antihistamine — ask your pharmacist or GP which one and what dose — handles the skin symptoms. Vomiting once after a new food is also fairly common and not in itself an emergency.
The red flags — what counts as anaphylaxis and means calling 999 right now:
- Swelling of the tongue, throat, or face going beyond the lips
- Difficulty breathing, wheezing, persistent cough, hoarse cry, or a strange high-pitched sound on breathing in
- Widespread hives all over the body, not just around the mouth
- Repeated vomiting
- Pale, floppy, unresponsive, or blue around the lips
- Sudden drowsiness or collapse
Lay the baby flat with legs raised (or on their side if vomiting), call 999, say the word "anaphylaxis." If the family already has an adrenaline auto-injector (EpiPen, Jext, Emerade), use it into the outer thigh through clothing if needed. Anaphylaxis on a first-ever exposure to a food is rare — the immune system usually needs to have met it before to react this strongly — but it can happen, which is why you stay home and watch for two hours rather than handing the baby to grandparents and going for a walk.
Higher-Risk Babies
A baby is in the higher-risk group if they have:
- Moderate to severe eczema (skin needing more than basic emollient, started before four months)
- An already-diagnosed food allergy (egg allergy is the classic flag for peanut risk)
- A sibling with peanut allergy is a softer flag — talk to your GP
These babies should see an allergy specialist or paediatric allergist before peanut or egg goes in. The specialist may do a skin-prick test or specific IgE blood test, and either green-light home introduction, do a supervised first dose in the clinic, or arrange a formal oral food challenge. The British Society for Allergy and Clinical Immunology (BSACI) publishes the protocol UK clinics use.
Mild eczema — the kind that responds to regular moisturiser — is not in this category. Home introduction on the standard timeline is fine.
Common Questions
"My baby has a streak of eczema after the egg — is that an allergy?" Hives that come up within minutes of eating and fade in an hour or two suggest IgE allergy. A general flare-up of background eczema a day later usually does not. If unsure, photograph it and show your GP or health visitor.
"Should I do skin-prick testing before introducing peanut?" No — not for a baby with no eczema and no other allergy signs. Routine pre-screening is not recommended and can produce false positives that lead to unnecessary avoidance.
"Does breastfeeding protect against allergy?" Continuing to breastfeed during the introduction window is associated with better tolerance, but breastfeeding alone is not enough — the baby still needs the foods directly.
Key Takeaways
Introduce the major allergens — peanut, egg, dairy, wheat, fish, soy, tree nuts — from around six months alongside other first foods. Delaying does not protect against allergy; the LEAP trial showed early peanut introduction cut peanut allergy by about 80% in high-risk babies. Offer one new allergen at a time, in the morning or at lunchtime, and watch for two hours. Most reactions are mild (a flush of hives around the mouth) and settle in an hour or two. Anaphylaxis on first exposure is rare. Babies with moderate-to-severe eczema or an existing food allergy should see an allergy specialist before peanut and egg go in.
