Introducing Allergens to Babies: UK Guidance and What to Know

Quick answer: Introduce the most common allergenic foods from around 6 months, once solid foods have started, rather than delaying — there is no benefit to waiting until after 12 months. Offer one allergen at a time with a 2–3 day gap, start with a very small amount during the day at home, and watch for at least 2 hours. Once tolerated, keep offering it regularly.

What parents need to know

Food allergy rates in UK children have risen significantly over recent decades, affecting around 5–8% of children. But research has shown something important: introducing common allergens early — rather than avoiding them — actually reduces the risk of allergy. This changed NHS and NICE guidance significantly.

The current NHS position

The NHS and NICE recommend introducing the most common allergenic foods from around 6 months, once solid foods have started, and to do so early rather than delaying. There is no benefit to waiting until after 12 months — in fact, late introduction may increase risk.

The 14 major food allergens regulated in the UK include:

• Peanuts
• Tree nuts (almonds, cashews, walnuts, etc.)
• Milk
• Eggs
• Wheat
• Soya
• Fish
• Shellfish
• Sesame
• Lupin, celery, mustard, sulphur dioxide/sulphites, molluscs

Which allergens are most important to introduce?

The highest-priority allergens to introduce early are:

• Peanuts (crushed or ground into food, or as smooth peanut butter spread onto food such as toast, never on its own)
• Hen's egg (well-cooked first, then soft-boiled once comfortable)
• Cow's milk (in food such as yoghurt or cheese; not as a main drink under 12 months)
• Wheat (bread, pasta, cereals)
• Tree nuts (finely ground, or as nut butters spread onto food, never on their own)
• Fish (cooked and soft)

How to introduce allergens safely

One at a time

Introduce allergens one at a time, with a gap of 2–3 days between new ones. This means if a reaction occurs, you can identify the cause easily.

Start small

Begin with a small amount, such as a little smooth peanut butter mixed into a food your baby already eats (never nut butter on its own), or a teaspoon of plain yoghurt. Then watch for any reaction for at least 2 hours.

Time of day

Introduce new allergens during the day, not before bedtime. This means you're alert to any reaction and your GP surgery or 111 is accessible.

At home, not out and about

Introduce in a familiar, calm environment where you can observe your baby closely.

What does an allergic reaction look like?

Mild reactions may include hives (red, itchy raised spots), mild redness around the mouth, or a runny nose.

Severe reactions (anaphylaxis) are rare but serious and include: sudden swelling of the lips, mouth, throat or tongue; breathing very fast, struggling to breathe, or wheezing; a tight throat or difficulty swallowing; blue, grey or pale skin, lips or tongue (on brown or black skin this may be easier to see on the palms of the hands or soles of the feet); being limp, floppy or not responding like they normally do; vomiting or sudden diarrhoea; or loss of consciousness. There may also be a swollen, raised or itchy rash.

If you suspect anaphylaxis, call 999 immediately.

Mild reactions may warrant a GP appointment to assess and possibly refer to an allergy specialist.

High-risk babies

Babies with severe eczema or an existing food allergy are at higher risk of developing additional allergies. The BSACI (British Society for Allergy and Clinical Immunology) recommends these families seek specialist advice before introducing high-risk allergens. Speak to your GP for a referral.

The NHS also advises that if your baby already has a diagnosed food allergy or eczema, or you have a family history of food allergies, eczema, asthma or hay fever, you should talk to your GP or health visitor before introducing foods that could trigger an allergic reaction.

Once introduced: keep going

Once your baby has successfully tolerated an allergen, continue to offer it regularly (ideally a few times per week). Stopping for an extended period can cause tolerance to be lost.

Frequently asked questions

When should you introduce allergens to a baby?

From around 6 months, once solid foods have started. The NHS and NICE recommend introducing common allergenic foods early rather than delaying, as there is no benefit to waiting until after 12 months.

How long should you wait between introducing new allergens?

Leave a gap of 2–3 days between each new allergen. Introducing them one at a time means that if a reaction occurs, you can identify the cause easily.

What are the signs of an allergic reaction in a baby?

Mild reactions may include hives, mild redness around the mouth, or a runny nose. Severe reactions (anaphylaxis) include sudden swelling of the lips, mouth, throat or tongue; breathing very fast, struggling to breathe or wheezing; difficulty swallowing; blue, grey or pale skin, lips or tongue; being limp, floppy or not responding like they normally do; vomiting or sudden diarrhoea; and loss of consciousness. Call 999 straight away if you see any of these.

What if my baby has severe eczema or an existing food allergy?

These babies are at higher risk of developing additional allergies. The BSACI recommends these families seek specialist advice before introducing high-risk allergens. Speak to your GP for a referral.