Baby Food Allergies During Weaning: A UK Parent's Guide

Food allergy in babies is one of the biggest anxieties around starting solids — and understandably so. But the science has shifted significantly over the past decade. Here's what the current UK guidance actually says and how to introduce allergens confidently.

The top allergens to introduce

The NHS and NICE guidelines identify 14 major allergens, but these are the ones to introduce intentionally during weaning:

1. Peanuts (as smooth peanut butter — never whole nuts)
2. Tree nuts (almond, cashew, walnut — as smooth nut butters)
3. Egg (well cooked: scrambled, hard-boiled)
4. Cow's milk (in food — yoghurt, cheese, in cooking; not as a main drink until 1 year)
5. Wheat (bread, pasta, oat products)
6. Soya (tofu, soya yoghurt, edamame)
7. Fish (white fish and oily fish)
8. Shellfish (prawns — cooked)
9. Sesame (tahini, hummus)

Early introduction reduces risk

The landmark LEAP Study (Learning Early About Peanut Allergy) changed guidance worldwide. It found that introducing peanuts to high-risk infants at 4–11 months reduced peanut allergy by 80% compared to avoidance. Similar findings apply to other allergens.

Current NHS guidance: introduce allergenic foods from around 6 months, alongside other first foods. Do not delay them.

Who is higher risk?

Babies with severe eczema or an existing egg allergy have a higher risk of peanut allergy. If your baby has severe eczema or a known food allergy, speak to your GP or allergy specialist before introducing peanuts — earlier, supervised introduction may be recommended (from around 4–6 months).

For most babies with no eczema or existing allergies, home introduction is appropriate.

How to introduce allergens safely

One at a time — introduce each new allergen separately so you can identify any reaction clearly.

In the morning or lunchtime — never just before bed, so you can observe your baby for 2 hours after eating.

Start small — a teaspoon mixed into food is enough for a first exposure.

Wait 2 hours before giving more, and watch for reaction signs.

If no reaction, give again the next day — and then aim to include it regularly in the diet. Consistent exposure after introduction is important; allergens introduced and then removed from the diet can still lead to allergy.

Signs of an allergic reaction

Mild to moderate (usually manage at home, call 111 for advice):

• Hives (raised, itchy redness) around the mouth or body
• Swelling around lips or face
• Runny nose, watery eyes
• Mild stomach symptoms: vomiting, loose stool

Severe — call 999 immediately:

• Difficulty breathing, noisy or wheezing breath
• Swelling of tongue or throat
• Pale, floppy, unresponsive baby
• Persistent vomiting
• Loss of consciousness

This is anaphylaxis. It is rare but can be life-threatening. Trust your instincts — if something seems seriously wrong, call 999.

Common misconceptions

"We have family history of nut allergy so I should avoid them." Current guidance says the opposite for most families — early introduction is recommended. A family history of allergy increases risk but does not mean your baby will be allergic, and avoidance does not reduce that risk.

"My baby had a rash once — they're allergic." A rash around the mouth after eating is often a contact reaction (acid from citrus, or saliva rubbing) rather than a true allergy. A true allergic rash is usually raised, itchy hives that spread beyond the contact area. Unsure? Contact your GP.

"I should introduce one allergen a week." You can go more quickly than this once you're through the first few days of weaning and baby is tolerating food well. Check with your health visitor or GP if you want to move faster.

What happens if my baby does have an allergy?

A GP referral to an allergy clinic or paediatric dietitian is the next step. Do not eliminate food groups without professional support — a dietitian will help ensure your baby's nutritional needs are met while managing the allergy.

Egg and milk allergies in infancy are often outgrown — many babies who react to milk or egg at 12 months are tolerating them by 4–5 years.

Peanut and tree nut allergies are more likely to be lifelong, though oral immunotherapy is now available on the NHS for some.

Keeping records

Log what you introduced and when — including any reactions, however mild. This is invaluable if you need to speak to a doctor later. TinyYears is ideal for this: log food alongside milestone notes so you have a clear record of early weaning.