Introducing allergen foods to babies
Common allergen foods can be introduced from around 6 months as part of weaning. Introducing them isn't something to avoid, but do it carefully. This summarises NHS advice.
Why early introduction is now recommended
For many years, parents were advised to delay the introduction of high-risk allergens, particularly peanuts, to reduce the chance of their baby developing an allergy. That guidance has been reversed. Research, most notably the LEAP (Learning Early About Peanut Allergy) trial, demonstrated clearly that introducing peanuts early in life significantly reduces the risk of peanut allergy developing, rather than increasing it. The LEAP study found that high-risk infants who were given peanut products from around 4 to 11 months had a substantially lower rate of peanut allergy by the age of 5 compared with infants who avoided peanuts entirely.
This evidence, along with research into other allergens, prompted a significant shift in clinical guidance. The NHS now recommends introducing all common allergens from around 6 months of age as a normal part of weaning, alongside other solid foods. There is no benefit in delaying their introduction beyond this point, and doing so may increase the risk of allergy. The key word in all of this is "around": every baby is different, and the NHS advises that solids should not be started before 17 weeks (around 4 months). Most babies are ready at around 6 months, showing signs such as being able to sit with support and hold their head steady, and showing interest in food.
The rationale for early introduction is thought to be connected to immune tolerance. Exposing the immune system to allergenic proteins early, while the gut and immune system are still developing, appears to help the body learn to treat those proteins as harmless. Delaying exposure, by contrast, may mean the immune system first encounters allergenic proteins through skin exposure (for example through inflamed eczema skin) rather than through the gut, and this alternative route of sensitisation appears to be linked to a higher risk of allergy. This is one reason why babies with moderate to severe eczema are considered higher risk and may benefit from specialist input before allergen introduction begins.
The common allergens and how to offer them
There are 14 allergens that are legally required to be declared on food labels in the UK. These are: cow's milk, eggs, cereals containing gluten (wheat, barley, and rye), peanuts, tree nuts (including almonds, hazelnuts, walnuts, cashews, pecans, pistachios, and macadamia nuts), fish, shellfish, soya, sesame, celery, lupin, mustard, molluscs, and sulphur dioxide (used as a preservative in some dried fruits and wines).
For parents weaning a baby, the most practically relevant allergens to introduce systematically are: cow's milk (offered as dairy foods such as full-fat yoghurt or cheese, not as a main drink before 12 months), eggs (cooked thoroughly, for example well-cooked scrambled egg), cereals containing gluten (wheat in bread, pasta, or baby cereals), peanuts (as smooth peanut butter with no added salt or sugar, or finely ground peanuts mixed into a puree), tree nuts (as smooth nut butters or ground nuts mixed into food), fish (well-cooked and boneless), soya (plain tofu, soya yoghurt, or soya-based formula if using), and sesame (as tahini or finely ground sesame paste mixed into food such as hummus).
Practical examples of a first portion: a small teaspoon of smooth peanut butter stirred into a fruit or vegetable puree; a teaspoon of well-cooked scrambled egg; a small taste of smooth hummus (which contains both sesame and sometimes legumes); a tiny flake of well-cooked white fish mixed into a meal. The important thing is to start with a genuinely small amount, particularly for any food you have not offered before.
A note on form: whole peanuts, whole tree nuts, and whole seeds must never be given to babies or children under 5 years old. The risk of choking is serious and real. Ground, smooth, or paste forms are safe when prepared correctly and offered in age-appropriate textures.
How to introduce allergens step by step
The NHS advises introducing allergens one at a time. This matters because if a reaction does occur, you need to be able to identify which food caused it. If you introduce three new allergens on the same day and your baby develops hives, you will have no way of knowing which food to avoid going forward.
Choose a day when your baby is well. Avoid introducing a new allergen when your baby has a cold, is teething badly, or is otherwise unwell, as this can make any skin reaction harder to interpret. Offer the new food at the start of a meal, in a small amount, at a time of day when you will be at home and able to observe your baby for at least two hours afterwards. You do not need to sit watching with a timer, but you should be present and attentive.
If no reaction occurs, wait two to three days before introducing the next new allergen. This waiting period allows you to identify any delayed reaction, which can sometimes appear a day or two after eating. Keep a simple note of what you introduced and when. Cubby's health section is a convenient place to log new foods alongside any observations.
Once a food has been tolerated without any reaction, it is important to keep offering it regularly, at least weekly. NHS guidance is explicit on this point: stopping an allergen after a successful introduction is not a neutral action. Reintroducing a food after a gap of weeks or months can increase the chance of sensitisation and, ultimately, allergy. Aim to build tolerated allergens into your baby's normal diet rather than treating the introduction as a one-off test.
There is no strict order in which allergens must be introduced. Many families find it practical to start with foods that are easy to prepare and commonly eaten in the household, such as egg or dairy, and then work through others over the following weeks. By the time your baby is around 8 to 9 months old, most of the key allergens should have been offered at least once.
Higher-risk families: when to speak to a doctor first
Most babies can have allergens introduced as part of normal home weaning without any special preparation or medical supervision. However, some babies are at higher risk of an allergic reaction, and for these families the NHS recommends speaking to a GP or health visitor before starting allergen introduction.
Higher risk means one of the following applies: the baby already has a diagnosed food allergy (even to a different food); the baby has moderate to severe eczema that is difficult to control with standard treatments; or the baby has a parent or sibling with the specific food allergy being introduced. If any of these apply, the GP or health visitor may refer the baby to a paediatric allergy specialist, who can arrange a supervised introduction in a clinical setting where any reaction can be managed immediately.
It is worth being clear about what does not automatically place a baby in the higher-risk category. A family history of non-food allergy, such as hayfever, asthma, or pet allergy, does raise the overall likelihood that a baby may develop allergies, but it does not on its own require specialist input before allergen introduction. Mild eczema that is well-managed with standard emollients and occasional topical treatments does not typically require a referral before starting allergens at home. If you are unsure which category your baby falls into, your health visitor is a good first point of contact.
For families in the higher-risk group, waiting for a referral can feel anxious. It is reasonable to ask your GP how long the wait is likely to be and whether there are practical steps you can take in the meantime, such as ensuring your baby's eczema is as well-controlled as possible before introduction begins.
Recognising mild and severe reactions
Most babies who are introduced to allergens do not have any reaction at all. For those who do, the majority experience mild symptoms that are uncomfortable but not dangerous. Knowing the difference between a mild reaction and a severe one means you can respond calmly and appropriately.
Mild reactions typically include: localised hives or redness around the mouth or on the face; mild swelling of the lips; a rash appearing on the body some time after eating; watery or slightly red eyes; or a runny nose. If you observe any of these, stop offering that particular food. Your baby does not need emergency treatment, but you should contact your GP within the next day or two. The GP may refer to an allergy service for further assessment, which could include a skin prick test or a supervised food challenge. In the meantime, avoid that food.
Severe reactions, known as anaphylaxis, are much rarer but are a medical emergency. The signs of anaphylaxis include: sudden and significant swelling of the lips, face, tongue, or throat; difficulty breathing, noisy breathing, or wheezing; your baby going pale, floppy, or unresponsive; persistent vomiting immediately after eating; or a combination of symptoms affecting more than one part of the body at the same time. If you observe any of these signs, call 999 immediately. Do not wait to see whether the symptoms resolve. Tell the emergency operator that you suspect anaphylaxis in an infant and what food was eaten.
After any allergic reaction, do not attempt to reintroduce that food at home without medical advice. The next exposure could produce a more severe reaction, and reintroduction should be managed under supervision.
Frequently asked questions
When can I give my baby peanuts?
From around 6 months, as smooth peanut butter (no added salt or sugar) or finely ground peanuts mixed into food. Never give whole peanuts to babies or children under 5 because of the choking risk.
What does a mild allergic reaction look like?
Redness or raised skin around the mouth, some hives on the body, mild lip swelling, or watery eyes. These reactions are uncomfortable but not dangerous. Note which food was introduced, contact your GP in the next day or two, and avoid that food until you have spoken to them.
Do I need to keep offering an allergen once my baby has tried it?
Yes. NHS guidance is clear that once a food is tolerated, it should stay in the diet regularly. Withdrawing an allergen for weeks or months after successful introduction can lead to sensitisation and increase the risk of allergy developing.
My baby has eczema. Should I talk to a doctor before introducing allergens?
Yes, if your baby has moderate to severe eczema that is difficult to control. Speak to your GP or health visitor first; they may refer to an allergy specialist. Mild eczema that is well-managed usually does not require specialist input before starting allergen introduction.
Log allergens as you go
Cubby's health section keeps allergies and reactions in one place, shareable with anyone caring for your baby.
Start free