Advice about when and how to introduce allergenic foods during weaning has changed significantly over the past decade, and the current recommendations — based on strong trial evidence — are almost the opposite of what parents were told a generation ago. Understanding what the evidence shows and how to introduce allergens safely and systematically is one of the most important aspects of the weaning process, particularly for families with a history of allergy or with a baby who has eczema.
Healthbooq supports parents with current, evidence-based guidance on introducing solid foods, including the allergen introduction approach recommended by NICE and BSACI for infants at standard and elevated allergy risk.
How Guidance Has Changed
Until the 2000s, guidance in the UK and internationally advised delaying the introduction of highly allergenic foods — particularly peanut and egg — beyond the first year or even the first several years. This advice was based on the hypothesis that avoiding early exposure would reduce the chance of allergy developing. Large-scale randomised trials, most notably the LEAP (Learning Early About Peanut Allergy) trial published in 2015, showed the opposite: early regular exposure to peanut in high-risk infants reduced the rate of peanut allergy by approximately 81% compared to avoidance. The EAT (Enquiring About Tolerance) trial added supporting evidence across multiple allergens.
Current NHS and BSACI guidance, endorsed by NICE, now recommends introducing allergens at the time of solid food introduction (around six months, not before four months), rather than delaying them.
The Fourteen Major Allergens
UK food labelling law identifies fourteen major allergens. The most clinically relevant for infants are: peanuts, tree nuts (almonds, cashews, walnuts, pecans, hazelnuts), hen's egg, cow's milk, wheat, fish, shellfish, sesame, and soya. Most childhood food allergies involve peanut, milk, egg, and wheat.
The Standard Approach: Introducing at Home
For the majority of infants — including those without eczema or family history of allergy — allergens can be introduced at home as part of normal weaning. The recommended approach is to introduce allergens one at a time, with a small amount first, waiting a few days before introducing the next new allergen, so that if a reaction occurs, the responsible food can be identified.
Practical forms: peanut can be introduced as smooth peanut butter (thinned with a little water, breastmilk, or formula and mixed into purée — never whole peanuts, which are a choking hazard); egg can be offered as well-cooked egg (scrambled, or as a thin omelette strip); cow's milk as part of cooked dishes (cheese, yoghurt, butter in cooking) — not as a main drink before twelve months; wheat in baby porridge, pasta, or bread.
The food should be given when the baby is well (not currently unwell), at the beginning of a meal (so the rest of the feed can be offered if a reaction occurs), during the day when the parent can observe for two hours after. A mild reaction such as a small localised rash around the mouth that resolves within minutes is common and does not necessarily require medical attention unless it spreads or is accompanied by other symptoms.
Signs of Allergic Reaction
Mild symptoms: redness or hives around the mouth or where food touched the skin; mild watery eyes or runny nose. These often do not require emergency treatment but should be discussed with a GP.
Moderate to severe symptoms (anaphylaxis): facial swelling, swelling of the lips or tongue, widespread hives, vomiting or diarrhoea combined with skin symptoms, breathing difficulty, unusual drowsiness, or collapse. These require an immediate call to 999.
Higher-Risk Infants
Infants with severe eczema — defined as eczema requiring regular use of prescription-strength topical corticosteroids — are at significantly elevated risk of food allergy. For these infants, BSACI guidance recommends allergen-specific skin prick testing or specific IgE testing before introducing peanut and egg, as their allergy risk is high enough that a home introduction could risk a serious reaction. A GP or paediatric allergist referral is appropriate before introducing these specific foods.
Infants who already have a confirmed food allergy should not have closely related foods introduced at home without specialist guidance.
Maintaining Exposure
Once an allergen is successfully introduced without reaction, current evidence supports continuing to offer it regularly — several times per week — rather than introducing it once and then not offering it again. Regular exposure appears to be important for the protective effect; tolerance can be lost if the food is not offered consistently.
Key Takeaways
Current evidence strongly supports the early introduction of common allergenic foods — including peanut, egg, cow's milk, wheat, fish, and sesame — at the time of solid food introduction, around six months, rather than delayed introduction as was previously advised. Early introduction is associated with reduced risk of food allergy developing, not increased risk. For most infants, including those with mild to moderate eczema, allergens can be introduced at home following standard guidance. Infants with severe eczema or an existing food allergy should be assessed by a specialist before introduction of the most relevant allergens.
