Introducing allergens is a concern I hear most often from parents in the middle of weaning. Not because it's the most complicated part nutritionally, but because the worry attached to it is so heavy. You're handing your baby a food that could, theoretically, cause a reaction. That's frightening, especially when the guidance has shifted noticeably over the past decade and not everyone's got the updated version.
So let me give you a clear picture of where the evidence sits now, and walk you through what I'd actually tell a parent sitting across from me at a clinic appointment.
Why early introduction matters
Until fairly recently, many families were advised to delay common allergens, particularly peanuts, until age 3. That advice has changed significantly, and the science behind the change is now well established.
What research has shown is that the immune system is actually better positioned to build tolerance when it encounters a new food protein early, from around 6 months (or earlier between 4-6 months), rather than later. Babies whose immune systems first meet peanut protein as a small, regular part of their diet are substantially less likely to develop an allergy to it than those who meet it for the first time at age 2 or 3. This finding has been replicated across multiple allergens, not just peanuts, and it now forms the basis of UK guidance. Think of this like closing the door on food allergy!
NHS Start for Life weaning guidance is clear on this, introduce allergens from the start of weaning alongside other first foods, not after them.
There are two situations where it's worth knowing this guidance is even more important. If your baby already has a known food allergy, or if they have significant eczema (particularly moderate to severe) it is recognised they are at higher risk of developing food allergy, so it can be helpful to speak to a GP, health visitor or allergy specialist about consideration of earlier introduction to certain allergens like egg and peanut before 6 months of age. Regardless, the advice across the board is not to delay, and for most families, though, early and regular is the right approach.
Which allergens to introduce, and when
Nine allergens account for the vast majority of childhood food allergies in the UK: peanuts, tree nuts (cashews, almonds, walnuts), cow's milk, eggs, wheat, sesame, soya, fish and shellfish. These are the ones to focus on during weaning.
From around 6 months. As you introduce solids, bring in the major allergens one at a time. A small amount is all you need, starting with small amounts and building up to a teaspoon of smooth peanut butter stirred into porridge, a tablespoon of soft scrambled egg, some yoghurt, a few spoonfuls of a wheat pasta dish, flaked fish in a sauce. Introduce each new allergen on its own rather than several at once, so that if a reaction appears you can pinpoint the cause. Advice currently suggests egg and peanut as the best options to get going with.
Timing can also be helpful to consider. Offer a new allergen in the morning or at lunchtime, not before bed, so you have a couple of hours to watch your little one afterwards. Do the first introduction at home rather than at nursery or a restaurant, where you have less control over what else they're eating.
From 9 months. Once your baby is managing a wider range of textures, it becomes easier to include allergens as a natural part of everyday meals rather than tracking them carefully. At this stage, balanced ready-made meals that already contain common allergens can take a lot of the effort out of maintaining variety.
My First Fish Pie brings together mixed white and red fish in a bechamel sauce with mashed potato and parsnip, so it covers both fish and dairy in a single mealtime. My First Pasta Bolognese uses British beef mince in a vegetable and tomato sauce with wheat pasta, and has a smooth texture that works well from this age.
Continue including each allergen ideally at least once a week once your baby has tolerated it without a reaction. There's no need to keep a formal log at this point. The goal is regular, varied exposure as part of normal family eating, not a checklist to work through with precision.
From 12 months to 3 years. Keep allergens in the diet consistently through the toddler years. This matters more than people realise. If a food is introduced, tolerated, and then quietly dropped from the rotation, there is a small possibility of sensitisation developing particularly in high risk children. Variety and regularity remain the right approach.
My First Mediterranean Veg Orzo, with orzo pasta in a vegetable and tomato cream sauce, is a reliable toddler meal that brings in both wheat and dairy without making a fuss of it. Blueberry Mini Muffins are a practical snack choice at this stage too: super soft, loaded with blueberry and banana, and a natural way to include eggs and wheat in something toddlers genuinely enjoy.
One firm preparation rule across all ages: whole nuts should never be given to children under 5 due to choking risk. Peanut butter must be smooth, and any tree nuts should be finely ground or offered as a thin nut butter.
What a reaction looks like, and when to act
Not every response to a new food is an allergic reaction. Babies often pull faces, gag on unfamiliar textures, or have looser stools with some new foods. These can be normal responses, not allergy signs.
An immediate allergic reaction typically appears within minutes to 2 hours of eating the food. The signs to watch for: hives or a blotchy rash appearing on the skin, swelling around the lips, eyes, or face, repeated vomiting after eating, or persistent distress that's out of proportion to the meal. If you see any of these, stop giving the food and seek advice from a health professional.
Anaphylaxis, a severe allergic reaction, is rare but requires emergency treatment. Signs include difficulty breathing, a swollen tongue or throat, sudden limpness, or loss of consciousness. Call 999 immediately if this happens. Don't wait to see if it passes.
The distinction I most often need to reassure parents about is mild redness or blotchiness around the mouth. This frequently happens with acidic foods like tomatoes or strawberries, or higher histamine foods like Aubergine and is not an allergic response. A true allergic reaction involves multiple body systems, not just local skin irritation.
Keeping it manageable on a busy week
Allergen introduction doesn't need to feel like a project. For most families, it's simply a matter of serving a varied diet from the start of weaning and not avoiding any food group out of habit or old advice.
Some families do find it helpful to keep a short note for the first fortnight, just a line per day about which new allergen was introduced and whether anything unusual happened. Once you're past the initial introductions, that level of tracking is no longer needed.
If your little one follows a vegetarian or vegan diet, talk to your health visitor about allergen variety sooner rather than later. The absence of dairy and eggs from a plant-based diet means intentional planning is especially worthwhile.
For the busier evenings, having a range of allergen-containing meals already in the freezer means your tot gets variety without it all having to come from scratch. Our Build Your Box lets you mix and match from the full range of dietitian-developed meals and snacks, made with real ingredients and suitable from 9 months. Good enough, often, is exactly enough.
