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Baby - Food intolerances

It can be hard to tell if your child has a food intolerance or an allergy. We look at signs of a food intolerance, what you can do to help and how to cope.

What is a food intolerance?

Having a food intolerance means the body finds it hard digesting a particular food or foods. This causes a reaction and unpleasant symptoms (NHS, 2019a). A food intolerance isn’t the same as a food allergy because no immune system reaction takes place (NHS, 2019a).

It can be hard to diagnose a food intolerance, as symptoms could be caused by something else and there are no tests for it.

What are the symptoms of a food intolerance?

Symptoms usually occur some time after eating the food. Compared with an allergic reaction, a larger amount of food is needed to trigger symptoms and these are never life-threatening.

The symptoms of a food intolerance are different to those of allergies and may include repeated episodes of:

  • diarrhoea
  • tummy pain
  • skin rashes and itching
  • passing wind often
  • bloating.

(NHS, 2019a)

The most commonly suspected intolerance in babies and small children is lactose intolerance.

What is lactose intolerance?

Lactose is a sugar found in all milks. It's made by the mother’s body and is not related to her diet (Australian Breastfeeding Association, 2017).

Lactose intolerance is not the same as cow's milk protein allergy. Someone with lactose intolerance does not make enough of the enzyme lactase, which is needed to digest lactose (NHS, 2019b).

This means undigested lactose ferments in the gut and produces acids and gases, resulting in liquid/frothy/green poos, farting and discomfort.

Primary lactose intolerance

Primary lactose intolerance is caused by a gradual decrease in lactase production, which happens as a child's diet becomes less reliant on milk and dairy products (NHS, 2019b). It is rare in babies (First Steps Nutrition Trust, 2019) and usually happens after the age of two years old (NHS, 2019b).

Some human populations have evolved ‘lactase persistence’ and will continue making lactase. This means they can digest milk and dairy products as adults (Mattar et al, 2012).

Secondary lactose intolerance

Secondary lactose intolerance is caused by a problem in the small intestine. It may be a temporary condition that can result from something disturbing the gut, such as gastroenteritis (a tummy bug) or a long course of antibiotics (NHS, 2019b).

The NHS suggests that parents continue to give their baby their usual milk. With an older child, parents may wish to exclude solid foods containing dairy products while the gut is recovering (NHS, 2019b).

Congenital lactose intolerance

This is a very rare inherited condition which means a baby will not produce any lactase (NHS, 2019b). It causes abdominal pain, diarrhoea, flatulence and/or bloating. 

This will be picked up in the early days after a baby is born and they will be prescribed a special formula milk (First Steps Nutrition Trust, 2019).

Developmental lactose intolerance 

Some babies born before 37 weeks of pregnancy may not yet be producing a lot of lactase. This will usually improve as the baby gets older (NHS, 2019b).

What should I do if I suspect a food intolerance?

If you think your child has a food intolerance, you can speak to your GP. A breastfeeding counsellor on our Infant Feeding Support Line may also be able to help (8am-midnight): 0300 330 0700.

Always check with your GP before eliminating foods from your child’s diet in the long term (NHS, 2019c). Most children who have primary or secondary lactose intolerance can consume small amounts of lactose without experiencing symptoms.

You may be referred to a dietician for nutritional advice because it’s important for young children to have certain nutrients in their diet. 

How to cope emotionally

If your little one has symptoms of a food intolerance, it can be very stressful. For practical and emotional support you can contact our Infant Feeding Support Line (8am-midnight): 0300 330 0700.

You can read about one mum's experience of having a child with food allergies and reflux here.

Your GP will be able to help you work out what may be causing your child’s symptoms and refer you to a specialist if necessary (NHS, 2019c).

While it can be tough getting to the bottom of the cause, most intolerances are mild and can be managed. Food manufacturers are getting better at catering for people with food allergies and intolerances, so there’s now more choice available. 

This page was last reviewed in December 2021.

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

You might find attending one of our NCT New Baby groups helpful as they give you the opportunity to explore different approaches to important parenting issues with a qualified group leader and other new parents in your area.

Make friends with other parents-to-be and new parents in your local area for support and friendship by seeing what NCT activities are happening nearby.

Act On Cows’ Milk Allergy

Anaphylaxis Campaign

National Eczema Association

Asthma UK

Australian Breastfeeding Association. (2017) Lactose intolerance and the breastfed baby. Available at: [Accessed 16th December 2021]

First Steps Nutrition Trust. (2019) Specialised infant milks in the UK.  Available at: [Accessed 16th December 2021]

Mattar R, de Campos Mazo DF, Carrilho FJ. (2012) Lactose intolerance: diagnosis, genetic, and clinical factors. Available at:  [Accessed 16th December 2021]

NHS. (2019a) Food intolerance. Available at: [Accessed 16th December 2021]

NHS. (2019b) Lactose intolerance causes. Available at:  [Accessed 16th December 2021]

NHS. (2019c) Treatment lactose intolerant. Available at: [Accessed 16th December 2021] 

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Baby - Food intolerances

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