Baby Allergen Introduction Guide UK 2026 — When and How to Introduce the 14 Allergens | Modern Parenting

Baby Allergen Introduction Guide UK When, How and in What Order to Introduce All 14

The complete UK guide to introducing allergens during weaning — covering why early introduction reduces allergy risk, the step-by-step protocol for each of the 14 major allergens, how to recognise reactions, and what to do differently for high-risk babies.

Updated January 2026● NHS & BSACI aligned● 18 min read From 6 months

⚠️ Medical guidance note: This guide follows NHS and BSACI recommendations current as of January 2026. If your baby has severe eczema, an existing diagnosed allergy, or a first-degree relative with a confirmed food allergy, consult your GP or paediatric allergist before introducing high-risk allergens (particularly peanut and egg). Do not use this guide as a substitute for medical advice for high-risk babies.

① Why Early Introduction Matters

The guidance on allergen introduction has changed significantly over the past fifteen years. Before approximately 2010, UK guidance advised delaying the introduction of high-risk allergens — particularly peanut and egg — until after the first year. The intention was precautionary. The outcome was the opposite of what was expected: rates of peanut allergy in UK children roughly tripled during the period of delayed introduction guidance.

The pivotal LEAP (Learning Early About Peanut allergy) trial, published in 2015, demonstrated that introducing peanut to high-risk infants between 4 and 11 months reduced peanut allergy by 81% compared to avoidance. Subsequent research across other allergens has supported the same principle: early, consistent exposure teaches the immune system to tolerate a food rather than respond to it as a threat.

Current NHS and BSACI guidance now recommends introducing all 14 major allergens from around 6 months — at the same time as other solid foods, not after them. Delaying allergen introduction is no longer recommended for healthy babies without specific medical risk factors.

② When to Start Allergen Introduction

Begin allergen introduction when your baby shows the three readiness signs for weaning — sitting supported with head control, coordinated hand-to-mouth movement, and reduced tongue-thrust reflex. This is typically around 6 months. Do not start allergen introduction before 17 weeks (4 months) regardless of readiness signs.

Allergens should be introduced during weaning, not after a separate delay. They do not need to be held back until Stage 2 or Stage 3 of weaning — first tastes and allergen introduction happen simultaneously from around 6 months. There is no sequence requirement that says vegetables must come before allergens — offer both in the first weeks of weaning.

📅 Introduce allergens on a weekday morning. Offer each new allergen at the start of the day when you will be at home for 2–3 hours to observe. A weekday morning means your GP surgery is open if you need telephone advice. Do not introduce a new allergen immediately before a nap, at the end of the day, or immediately before leaving the house.

③ The Step-By-Step Protocol

Choose one new allergen Introduce one allergen at a time. Do not introduce two new allergens on the same day — if a reaction occurs, you need to know which allergen caused it.

Check the baby is well Do not introduce a new allergen if the baby has a cold, fever, eczema flare, or any acute illness. Wait until the baby is clearly well before introducing each new allergen.

Offer a small amount at the start of a meal A small taste — approximately ¼ teaspoon — is sufficient for the first introduction. Offer it at the beginning of the meal so you can observe clearly before the baby is tired from eating. Mix into familiar food (e.g. smooth peanut butter thinned into puree) if the baby is resistant to unfamiliar flavours alone.

Wait and observe for 2–3 hours Stay at home after introducing each new allergen and watch for any signs of reaction. Most allergic reactions occur within 30–60 minutes. Some reactions (particularly eczema flares) may appear hours later — note any changes and report to your GP.

Continue offering if no reaction If there is no reaction, offer the same allergen again within the following days — and continue to offer it regularly thereafter. Tolerance requires ongoing exposure: an allergen introduced once and then avoided for months may cause a reaction when reintroduced. Once successfully introduced, include the food in the baby’s diet regularly (at least weekly).

Wait 3–5 days before introducing the next allergen Allow 3–5 days between introducing each new allergen. This gives time to observe for delayed reactions and ensures you can attribute any reaction to the correct food. You do not need to wait this long between non-allergen foods — only between new allergens.

④ All 14 Major Allergens — How to Introduce Each

Allergen 01 Peanuts 🥜 Smooth peanut butter thinned with water or breast/formula milk to a runny consistency. Offer ¼ tsp mixed into vegetable puree or on a spoon. Never give whole peanuts to under-5s (choking risk). Crunchy peanut butter chunks are also inappropriate.

Allergen 02 Hen’s egg 🍳 Well-cooked scrambled egg or hard-boiled egg mashed into puree. British Lion stamped eggs can be offered runny; all other eggs must be fully cooked for babies. Egg white and yolk should both be included — allergy can be to either protein.

Allergen 03 Cow’s milk 🧀 Full-fat yoghurt, cream cheese or soft cheese mixed into puree or as a finger food. Cow’s milk itself should not be given as a main drink before 12 months — but dairy products as ingredients are introduced from 6 months. CMPA (cow’s milk protein allergy) is the most common food allergy in UK infants — symptoms may be delayed up to 72 hours.

Allergen 04 Tree nuts 🧁 Smooth almond, cashew or hazelnut butter thinned to runny consistency. Introduce tree nuts individually if possible — allergy to one tree nut does not guarantee allergy to all. Never whole or roughly chopped nuts. Mixed nut butter is acceptable after individual nuts have been introduced.

Allergen 05 Wheat (gluten) 🍞 Soft toast finger, well-cooked pasta, porridge made with oats. Wheat is one of the easiest allergens to introduce through everyday foods. Gluten includes wheat, barley, rye and oats. Coeliac disease (an immune response to gluten) is not the same as wheat allergy and has a different onset pattern — discuss with GP if concerned.

Allergen 06 Soya 🫘 Silken tofu mashed into puree, well-cooked edamame (mashed), or a small amount of soy sauce in cooking (note: soy sauce is also very high in salt — use a tiny amount in cooking only). Soya allergy often co-occurs with cow’s milk allergy.

Allergen 07 Fish 🐟 Well-cooked flaked white fish (cod, haddock) or oily fish (salmon, trout) mixed into puree or as a soft finger food. Remove all bones carefully before offering. Oily fish is also a key iron source — up to 2 portions per week is recommended during weaning. Introduce white fish and oily fish separately as distinct allergens.

Allergen 08 Shellfish (crustaceans) 🦐 Small amount of thoroughly cooked prawn, crab or lobster mashed into puree. Must be very well cooked — raw shellfish should not be given to babies. Shellfish allergy is among the most likely to be permanent (not outgrown). Separate from molluscs (see below).

Allergen 09 Molluscs 🐚 Thoroughly cooked squid, mussels or scallops mashed into puree. Less commonly consumed in UK baby diet but still one of the 14 regulated allergens. Introduce separately from crustacean shellfish as they are biologically distinct allergens.

Allergen 10 Sesame 🧆 Tahini (sesame paste) thinned with water, mixed into hummus-style puree. A small amount of sesame oil in cooking is also an option — though cold-pressed sesame oil retains more protein than refined oil. Sesame allergy rates are rising in the UK. Hummus contains both sesame (tahini) and chickpea — use plain tahini for the first sesame introduction.

Allergen 11 Celery 🥬 Celery stalks well-cooked and pureed, or a small amount of celeriac (celery root) in a puree or mash. Celery is less commonly eaten as a standalone baby food — cooking it into a vegetable puree with other vegetables is the most practical approach. Celery allergy is more common in continental Europe than the UK but is still one of the UK’s 14 regulated allergens.

Allergen 12 Mustard 🌿 A very small amount of mild prepared mustard mixed into a savoury puree. Mustard seeds ground into food or a tiny amount of mustard powder in cooking also works. Prepared mustard is typically high in salt and vinegar — use a tiny amount in cooking rather than as a condiment.

Allergen 13 Lupin 🫘 Lupin flour used in baking (some gluten-free breads and pastries contain lupin flour — check labels). Lupin seeds or beans are the less common route. Check bread and pastry labels as lupin is a common additive in gluten-free products. Lupin is a legume and can cross-react with peanut allergy — if your baby has a peanut allergy, introduce lupin only under medical guidance.

Allergen 14 Sulphur dioxide (sulphites) 🍇 Dried fruit (raisins, sultanas, apricots) is the most practical sulphite-containing food for babies — mash or chop finely for the first introduction. Some fruit juices and commercial baby foods also contain sulphites — check labels. True sulphite allergy is rare in infants. The reaction in sulphite-sensitive individuals is typically respiratory rather than skin-based.

⑤ Recognising Reactions

Most allergic reactions in babies are mild and localised — a rash around the mouth, mild hives on the skin, or slight swelling of the lips. A small number of reactions are severe (anaphylaxis). Knowing the difference between mild and severe reactions, and how to respond to each, is the most important knowledge for any parent undertaking allergen introduction.

Mild reaction — monitor closely, call GP

●Rash or hives around mouth or on skin

●Mild swelling of lips or tongue (not throat)

●Runny nose or watery eyes

●Vomiting or diarrhoea (alone, without other symptoms)

●Eczema flare appearing 2–24 hours after introduction

●What to do: stop offering the food, note symptoms, call GP surgery for advice. Do not reintroduce without medical guidance.

Severe reaction (anaphylaxis) — call 999 immediately

●Difficulty breathing, wheezing or stridor (high-pitched breathing)

●Swelling of tongue or throat

●Sudden severe pallor or going limp

●Loss of consciousness

●Sudden widespread hives combined with any respiratory symptom

●What to do: call 999 immediately, state you suspect anaphylaxis. If an adrenaline auto-injector is prescribed, use it. Do not wait to see if symptoms improve.

🩺 Anaphylaxis is rare during allergen introduction. The vast majority of allergic reactions during weaning are mild skin reactions. However, knowing the signs of anaphylaxis and having the 999 number ready is sensible precaution. The Anaphylaxis Campaign (anaphylaxis.org.uk) has free resources on recognising and responding to severe allergic reactions in children.

⑥ High-Risk Babies — A Different Approach

The standard allergen introduction protocol above is appropriate for healthy babies without specific risk factors. A different, medically supervised approach is recommended for babies in higher-risk categories.

Who is considered high-risk?

Babies with severe or moderate eczema (not mild), babies with a confirmed existing food allergy, and babies with a first-degree relative (parent or sibling) with a confirmed food allergy are considered higher risk. For these babies, allergen introduction — particularly peanut and egg — should be discussed with a GP or paediatric allergist before beginning.

The LEAP trial approach for peanut in high-risk babies

For babies with severe eczema or existing egg allergy, the LEAP trial protocol involves skin-prick testing to peanut before oral introduction. If the skin-prick test is negative, home introduction follows the standard protocol. If positive but below a certain threshold, a supervised oral food challenge in a hospital or allergy clinic is recommended. This does not mean peanut introduction is avoided — it means it is done with appropriate medical supervision for the small number of babies who are already sensitised.

If you believe your baby may be in a high-risk category, ask your GP for a referral to a paediatric allergy service. NHS allergy services are available in most regions, though waiting times vary. The Allergy UK helpline (01322 619 898) can provide guidance while awaiting a referral.

The key message

Introduce all 14 allergens early, individually and consistently. Early introduction reduces allergy risk — delay increases it.

The evidence is now clear that early allergen introduction is protective, not risky. The anxiety most parents feel when introducing allergens for the first time is understandable — but the risk of not introducing them is higher than the risk of introducing them with appropriate precautions. Follow the protocol: one allergen at a time, in the morning, when the baby is well, with observation afterwards. Once each allergen is successfully introduced, continue offering it regularly. Tolerance requires maintenance.

For healthy babies without risk factors, this guide covers everything you need. For babies with significant eczema, an existing allergy, or a close family member with a confirmed food allergy — speak with your GP before starting, and ask for an allergy referral if needed. The Allergy UK website (allergyuk.org) and the BSACI patient information pages are reliable resources for additional detail.

Frequently Asked Questions

In what order should I introduce allergens?+

There is no required order. Current guidance does not specify a sequence for the 14 allergens. Many parents start with the highest-priority allergens from a prevalence perspective — peanut, egg and cow’s milk are the three most common food allergies in UK infants and are sensible early priorities. After those three, introduce the remaining allergens in whatever order is practical given your family’s diet. Aim to have all 14 introduced by 9–10 months, while continuing to offer each regularly.

My baby had a rash around the mouth after eating tomatoes — is this an allergy?+

Possibly not. Rash or redness around the mouth in response to acidic foods (tomatoes, citrus, strawberries) is often a contact irritation rather than a true allergic reaction — the acid directly irritates the skin around the mouth without triggering an immune response. True food allergy rashes typically appear on the skin beyond the immediate mouth area and may be accompanied by other symptoms. If the rash is only around the mouth, appears immediately on contact and resolves quickly, it is likely irritation rather than allergy. If you are unsure, photograph the reaction and discuss with your GP.

What if my baby refuses the allergen food?+

Mix small amounts into familiar foods the baby already accepts. A tiny amount of thinned peanut butter mixed into sweet potato puree, egg mixed into vegetable mash, or tahini mixed into a savoury puree is equally effective for introduction purposes as offering the allergen alone. The immune system’s exposure to the protein is the important factor — not whether the baby knows they are eating it or accepts it willingly.

If my baby tolerates an allergen once, do I need to keep offering it?+

Yes — this is critical and one of the most commonly missed points in allergen introduction. Tolerance to a food requires ongoing exposure. A baby who successfully tolerates peanut at 6 months but then has no peanut for 3–4 months may react when peanut is reintroduced, because the tolerance mechanism requires maintenance. Once each allergen is introduced successfully, include it in the baby’s diet at least weekly. Regular exposure — not just a one-off introduction — is what builds lasting tolerance.

Guidance follows NHS and BSACI recommendations current as of January 2026. This guide does not constitute medical advice. For high-risk babies, always consult your GP or paediatric allergist before allergen introduction. Allergy UK helpline: 01322 619 898. Anaphylaxis Campaign: anaphylaxis.org.uk.