The guidance on introducing allergenic foods to babies changed significantly following the publication of the LEAP (Learning Early About Peanut allergy) trial and subsequent research. For decades, parents were advised to delay introduction of high-risk foods such as peanuts, tree nuts, and egg. The evidence now shows the opposite: early, regular introduction of these foods reduces allergy risk rather than increasing it.
Understanding the current evidence, who is considered high-risk, and how to introduce allergens safely in practice allows parents to navigate this aspect of weaning with evidence-based confidence.
Healthbooq provides parents with evidence-based guidance on weaning and food introduction, including the most current recommendations on allergen introduction.
The Fourteen Major Allergens
UK food labelling regulations require that fourteen allergens be declared in pre-packaged food: celery, cereals containing gluten (wheat, rye, barley, oats), crustaceans, eggs, fish, lupin, milk, molluscs, mustard, peanuts, sesame, soybeans, sulphur dioxide/sulphites, and tree nuts. Of these, the most commonly implicated in IgE-mediated food allergy in UK children are milk (cow's milk), egg, peanut, tree nuts, fish, wheat, and sesame.
The Evidence for Early Introduction
The LEAP trial (2015) was landmark: infants with severe eczema and/or egg allergy — historically considered high-risk for peanut allergy — were randomised to early peanut introduction (from four to eleven months) or peanut avoidance. At five years, the early introduction group had an 81% reduction in peanut allergy compared to the avoidance group. This overturned decades of advice.
Subsequent trials and meta-analyses have confirmed similar findings for egg and, to a lesser degree, other allergens. The proposed mechanism involves immune tolerance through oral exposure: early mucosal (gut) exposure to food proteins promotes tolerance, while sensitisation through inflamed skin (as in eczema) without prior oral exposure may drive allergy.
Current UK Guidance
NHS and BSACI (British Society for Allergy and Clinical Immunology) guidance now recommends that all babies, including those at higher risk, should have the common allergenic foods introduced from around six months, alongside the general introduction of solid foods. For babies with mild to moderate eczema, the same six-month approach applies. For babies with severe eczema or existing egg allergy, specialist paediatric allergy input is recommended before peanut introduction, as these babies may have already been sensitised.
Practical Introduction
When introducing a new allergen for the first time: offer it at home (not nursery or while travelling); offer it during the day so you can observe for two hours after; start with a small amount and increase over subsequent days; introduce one new allergen at a time rather than several simultaneously so that if a reaction occurs the cause is identifiable.
Signs of an allergic reaction to watch for: hives (red raised itchy skin welts); swelling — particularly of the face, lips, or tongue; vomiting; difficulty breathing; unusual drowsiness or pale and floppy appearance. A reaction involving the airway or cardiovascular system (anaphylaxis) requires an emergency 999 call.
Once a food has been tolerated, continue to include it in the diet regularly — regular exposure is required to maintain tolerance.
Key Takeaways
The evidence on food allergy prevention has shifted substantially in the past decade. Early introduction of allergenic foods — including peanut and egg — during the weaning period (from around six months, or from four to six months in high-risk infants) is now recommended as allergy-preventive rather than allergy-causing. Delaying introduction of allergens beyond twelve months is associated with higher, not lower, allergy rates. High-risk infants (with severe eczema or existing egg allergy) should have specialist input before peanut introduction. For standard-risk babies, allergens should be introduced one at a time, at home, during the day, watching for reactions for two hours.
