Introducing allergens during weaning

Last week Anaphylaxis UK celebrated National Weaning Week 2025—a time dedicated to supporting families as they introduce solid foods to their babies. We marked the occasion by publishing a podcast, offering practical, evidence-based information on safely introducing common allergens during weaning.

Weaning is an important milestone in a baby’s development. While it’s often an exciting stage, it can also bring many questions and concerns—particularly around food allergies. 

At Anaphylaxis UK, we’re here to support you to help make weaning safe, smooth, and enjoyable for your family.

What is weaning?

Weaning, or complementary feeding, is the gradual process of introducing solid foods alongside your baby’s usual breast milk or formula. The NHS guidance currently recommends starting weaning at around six months of age, when milk alone no longer meets all your baby’s nutritional needs. During this period, babies should continue their usual milk feeds while exploring a variety of new foods, including common allergens.

Introducing allergens: what parents need to know

It’s normal to worry about allergies, but research shows that introducing common allergenic foods (like egg and peanut) from around six months of age may help reduce your baby’s risk of developing allergies to these foods, and that delaying the introduction of allergens beyond 6-12 months increases the risk of developing allergies.

This means that when you and your baby are ready, and you have started to offer them small amounts of vegetables, fruit, starchy foods, and proteins, you can start introducing common allergens. These include:

• Cow’s milk (in cooking or as yoghurt)
• Well-cooked egg
• Peanut and tree nuts (as smooth, diluted nut butter or very finely ground-never whole or coarsely chopped)
• Soya
• Wheat and other gluten-containing grains
• Fish and seafood (well-cooked)
• Sesame and other seeds (finely crushed or ground)

The British Society of Allergy and Clinical Immunology (BSACI) guidance provides further information on how these different foods should be introduced.

While food allergies can occur with any food, the above foods are some of the more common allergens to watch out for in young children – especially egg, cow’s milk and peanut, which are the most common in babies and toddlers.

How to introduce allergenic foods safely:

• Introduce top allergens one at a time, using a very small amount (e.g., a quarter to half a teaspoon), and gradually increase over a few days. Once tolerated, they can be combined.
• Go at your baby’s pace-some take to solids quickly, others need more time. If your baby doesn’t seem interested, try again on another day.
• Mix the allergen into your baby’s usual milk, pureed vegetables, or a familiar food.
• If your baby tolerates an allergen, keep offering it regularly (at least once a week) to help maintain tolerance.
• Only try new allergens when your baby is healthy and their skin is in good condition, making it easier to spot any reactions.
• Start new foods early in the day so you have time to spot any reaction.
• Stay with you baby when feeding them.
• If you are struggling to feed your baby these foods, speak to your health visitor or GP. You may need to be referred to a dietitian.
• If your baby is considered high-risk for allergies, or already has a known food allergy, consult a healthcare professional before introducing new foods.
• Spoon feeding can help babies with severe eczema by reducing skin contact with allergens.
• Keep mealtimes relaxed and positive – it is a time to be enjoyed! Be allergy aware but remember that most babies will not have an allergic reaction, and most reactions are mild.
• Never cut out major food groups without professional advice, as this can affect your baby’s nutrition.

Introducing allergens in high-risk babies

Babies with severe eczema or a known food allergy are at higher risk of developing further allergies. Recent studies suggest that introducing common allergens like egg and peanut earlier, between 4–6 months, may reduce the risk of developing allergies in these high-risk babies. However, always speak to a healthcare professional before introducing allergens early-they can help assess risk, discuss if allergy testing is needed, and ensure eczema is well controlled before you start.

Allergy symptoms: what to watch for

Allergic reactions usually happen within minutes but can happen up to two hours after eating a food. 

Mild – moderate symptoms might include:

• Swollen lips, face, or eyes
• Hives or itchy skin rash
• Red, itchy, watery eyes
• Sneezing, runny or blocked nose
• Vomiting or tummy pain

If your baby experiences these symptoms, you can dial 111 for advice or speak to a healthcare professional.

Signs of a serious reaction (anaphylaxis) are rare but can include:

• Difficulty breathing, persistent cough, or wheezing
• A change in cry (hoarse)
• Swelling of the tongue or throat
• Pale, floppy, or suddenly very sleepy baby
• Collapse or unconsciousness

If you see these symptoms, call 999 immediately.

If your baby has had any allergic symptoms to a new food, stop giving that food and seek advice from a healthcare professional before trying it again.

Remember: Most babies enjoy weaning without any problems, and early, regular introduction of allergenic foods can help prevent allergies. For more support, visit Anaphylaxis UK’s weaning guide, the BSACI weaning guide, and listen to our new podcast with paediatric specialist dietitian Karen Wright: Infant weaning & allergies: how to introduce allergens safely and prevent food allergies.