How to Introduce Common Allergens to Children

When weaning your baby, it’s difficult to know when to introduce them to potential allergens, and how to do so safely. Nuts, soy, egg, and cow’s milk are all common triggers for serious food allergies and should be given to young children in small doses to check whether they have a reaction.

Find out how to safely test whether your child has any reaction to common food allergens, if allergens can pass through breast milk, and which foods to watch out for when feeding your baby.

Common Food Allergy Triggers

The most common causes of food allergies in children are:1

  • Milk – cow’s milk and formula. If a child is allergic to one, they’re likely to have a reaction to both
  • Egg
  • Wheat
  • Soya
  • Peanuts

Besides the most common culprits, watch your child when they eat or come into contact with these foods in case of an allergic reaction:1

  • Fish and shellfish
  • Gluten
  • Celery and celeriac
  • Sesame seeds
  • Pine nuts
  • Mustard
  • Fruits and vegetables – certain kinds can cause swelling to the lips, mouth and throat, known as ‘oral allergy syndrome’
  • Meat – some people are allergic to only one type of meat while others can suffer reactions (usually skin irritation) to all kinds

Can Allergens Transfer to Babies Through Breastfeeding?

Yes – even if the baby has never eaten solid food, allergens can pass from mother to child through breast milk. For instance, if the baby has a peanut allergy and the mother eats peanuts, the baby can suffer a reaction after breastfeeding. In this case, the mother is advised to remove the offending foods from her diet while breastfeeding.2,3

Like with any allergies, the child’s reaction to allergens in breast milk can range from mild (e.g. diarrhoea or constipation) to severe (in rare cases, anaphylaxis).3 If your baby has an allergic reaction, seek immediate medical help.

Introducing Food Allergens to Children Safely

Learn about some of the key points for introducing common food allergens like soy, sesame, egg and peanut butter to children:4

  • It’s important to introduce babies to common allergy-causing foods (smooth nut butter, well-cooked egg, milk, etc.) by one year of age, as studies have shown that delayed introduction can increase the risk of a food allergy developing. Babies should be exposed even if their parents, other family members, or siblings have allergies to a food.
  • Only give your baby one possible allergen per meal to easily identify the problem food if there is a reaction.
  • Once a common allergenic food is introduced and there is no reaction, keep giving it to your child on a regular basis, e.g. twice a week. Trying once and then avoiding the food may increase the chance of a food allergy developing.
  • At first, rub a tiny bit of common allergy-causing foods (like well-cooked egg or smooth nut butter) inside your baby’s lip. If there is no reaction after a few minutes, proceed with giving them a small amount of the food to eat.
  • Try mixing small amounts of food, like a quarter of a teaspoon of hard-boiled egg or nut butter, into a vegetable puree.
  • Gradually increase the amount of the potential allergen – e.g. a few days after trying the quarter teaspoon, try half a teaspoon mixed into a puree.

If your baby has a reaction when trying a common allergenic food, such as facial swelling, hives, or vomiting, immediately remove the food and seek medical advice.

If your baby displays signs of anaphylaxis, such as difficulty breathing, becoming pale and floppy, or a swollen tongue, call an ambulance.4

What is the Milk Ladder?

One of the most common food allergies to affect children and babies is cow’s milk. If a milk allergy is identified and you are breastfeeding, you will be encouraged to keep doing so while cutting cow’s milk and dairy out of your diet.5 If your baby is formula-fed, your doctor will advise which kind is best.

Fortunately, many babies grow out of their cow’s milk allergy in early childhood. Under the supervision of your doctor, cow’s milk can be gradually re-introduced to your child when the time is right.5 This is done using the “milk ladder”.

When your GP says it’s safe to re-introduce cow’s milk using the milk ladder method, the process will look like this:6

  • Before starting, have a child-appropriate antihistamine at hand, like Piriton Syrup (always check the pack to ensure your child is old enough to use it and to know the dosage for their age).
  • Begin by testing some cow’s milk on your child’s skin, e.g. on their cheek or another place where eczema may flare up if there is a reaction. If there is no reaction after a few hours, progress to trying foods made using milk.
  • Give your child one malted milk biscuit containing milk powder (not whey powder). If using shop-bought biscuits, check they contain milk and not whey. Gradually build up to three biscuits.
  • Next try half a muffin, building up to a whole muffin.
  • Move on to half a pancake, then a whole pancake. (Note that pancakes contain less milk than muffins but are cooked for a shorter time.)
  • If no reaction is present with the above, try giving your child 15 grams of hard cheese, like cheddar. If that is tolerated, next try 15g baked cheese, such as on pizza.
  • Lastly, give your child 100ml of pasteurised cow’s milk or infant formula powder mixed in with their current milk replacement. If there is no reaction, replace all of their milk replacement with pasteurised cow’s milk or infant formula.

Sometimes children can tolerate milk in foods but not as a drink. Reactions to drinking milk can appear within 48 hours. If your child has a reaction to drinking milk, but not to smaller amounts of milk in foods, you should include the foods in their diet up to the amount that they remain reaction-free. Drinking milk can be re-introduced again at a later stage.6

At any stage in the milk ladder, if there is a reaction, stop the test immediately but try again in six months.6


  1. NHS. Causes – Food allergy. Accessed 07/02/2022.
  2. M F Martín-Muñoz, F Pineda, G García Parrado, D Guillén, D Rivero, T Belver, S Quirce. Food allergy in breastfeeding babies. Hidden allergens in human milk. Accessed 07/02/2022.
  3. BabyMed. Breastfeeding and Food Allergies. Accessed 07/02/2022.
  4. ASCIA. How to Introduce Solid Foods to Babies for Allergy Prevention - Frequently Asked Questions (FAQ). Accessed 07/02/2022.
  5. AllergyUK. Does My Child Have a Cow's Milk Allergy?. Accessed 07/02/2022.
  6. NHS. The Milk Ladder - has my baby grown out of Cow's Milk Protein Allergy?. Accessed 07/02/2022.