Lactose intolerance in babies

Lactose intolerance in babies, whilst very rare, can happen. There are a number of symptoms to look out for, many of which are the same or very similar to a cow’s milk allergy, or other common feeding problems such as baby reflux, constipation or colic. It’s very important to understand the difference to ensure that you get the right advice, diagnosis and treatment. 

Here we’re exploring what lactose intolerance is, the causes, symptoms and signs of lactose intolerance in babies, as well as what it means for your baby’s diet.  

What is lactose intolerance?

Lactose is a sugar naturally found in milk and most other dairy products. To digest lactose, the body breaks it down using lactase, a digestive enzyme produced in the gut1. Lactose intolerance occurs when the body is unable to produce enough lactase, resulting in a number of unpleasant symptoms after eating any foods containing lactose. It’s important to know that lactose intolerance isn’t a milk or food allergy2

What are the causes of lactose intolerance?

There are three main types of lactose intolerance3:

Primary lactase deficiency

This occurs when the body’s natural lactase production decreases. This could be because of age, or in response to reducing the amount of dairy products that you eat. A primary lactose intolerance is very uncommon in babies under two years of age, as they’re still likely to be consuming plenty of milk through breast or formula feeding.

Secondary lactase deficiency

An often temporary intolerance to lactose, this is caused by damage to the gut, because of a stomach bug or infection, undiagnosed coeliac disease, or a long course of antibiotics, for example.  

Sometimes, if your baby has been unwell with gastroenteritis, this can result in lactose intolerance. If your child has been diagnosed with gastroenteritis, and they’ve been experiencing diarrhoea for longer than two weeks, then it’s worth having a chat with your GP to rule out lactose intolerance4.

Congenital lactase deficiency

This is a very rare, genetic form of lactose intolerance, where babies are born without, or with very low amounts of, lactase due to a genetic fault they inherit. 

Other causes of lactose intolerance in babies

If your baby was born prematurely, they may be more susceptible to lactose intolerance because their small intestine isn’t developed enough at birth. However, in most cases, this condition usually improves as your baby gets older.

Symptoms of lactose intolerance in babies

As we’ve said above, the signs of lactose intolerance in babies can be similar to those of other conditions, meaning that it’s sometimes hard to identify. However, common symptoms include2:

Your baby’s symptoms can start anywhere between a few minutes and a few hours of them consuming food that contains lactose1.  

Lactose intolerance or a cow’s milk protein allergy?

Because the symptoms of lactose intolerance are so similar to those of a cow’s milk protein allergy, it can be very difficult to distinguish one from the other. They are, however, different.

Whereas a cow’s milk protein allergy is caused by an immune reaction to the proteins that milk contains, lactose intolerance is caused when the body doesn’t produce enough lactase​5.

If you’re concerned that your baby has either a cow’s milk protein allergy or is experiencing lactose intolerance, always seek guidance from your GP, who may refer your baby to a dietician to help you manage your baby’s condition.

What to expect from your lactose intolerant baby’s poop

Whilst loose, watery stools are common in babies with lactose intolerance, they can be a symptom of other things, too. As such, if your baby starts having runnier poos than usual, this doesn’t necessarily mean that they're lactose intolerant.

Remember that it’s not unusual for newborn babies to have the odd runny poo, and every baby is different when it comes to their pooing habits. Once you get to know their toilet habits, you’ll know what’s normal, and what’s not so normal, for your baby. Take a look at our poop chart to learn more.

What to do if your baby is lactose intolerant

If you think your baby is having digestive trouble, you should visit your GP who can help with a diagnosis. It might be that your baby is referred to a paediatric dietician for more expert care. 

If you suspect that your baby is lactose intolerant, you shouldn’t make any changes to your baby’s diet unless instructed to do so by your doctor or other healthcare professional. This is because it’s important to ensure that your baby continues to get all the nutrients they need. Of particular importance is calcium, which the body often gets from food which also contains lactose. If there’s insufficient calcium in the diet, this can affect normal bone development3.

Any recommended treatment will depend on how severe your baby’s lactose intolerance is. It might be that your baby is able to tolerate small amounts of dairy and other foods containing lactose without experiencing any symptoms at all2.

If you’re breastfeeding, you should continue doing so, as it has numerous benefits for both you and your baby. It’s worth knowing that the amount of lactose in your own diet isn’t related to your baby’s intolerance, so eliminating lactose from your diet won’t make a difference here. If you think your baby may be reacting to the lactose in your breast milk, the best thing to do is seek advice and guidance from your GP.

If your baby is formula fed, your GP or paediatric dietitian may recommend a lactose-reduced or lactose-free infant formula milk for your baby.

If a lactose intolerance is managed and your baby is monitored, it won’t affect their development. Identifying lactose intolerance early means that your baby will feel well again and get the nutrients they need for this stage of their development and their future growth.

Foods containing lactose and their alternatives

Because lactose is found in so many food staples, you might be wondering just how much lactose some of them contain. Take a look at the lactose levels of some common foods7:

  • Glass of milk (100ml) - 4.6g lactose
  • Yogurt whole milk (100g) - 4.7g lactose
  • Cheddar cheese (100g) - 0.1g lactose
  • Cottage cheese (100g) - 3.1g lactose
  • Rice pudding (100g) - 3.9g lactose
Food TypeFoods containing lactoseLow-lactose alternatives
MilkMilk solids, Condensed milk, Modified milk, Evaporated milk, Skimmed milk powder, Buttermilk

Lactose-reduced and lactose-free formulas (e.g. Aptamil Lactose Free).

Rice, oat, almond, hazelnut, coconut, quinoa and potato milks

(Important note: only formula milk should be used for babies under one year. Children under 5 years old shouldn't have rice drinks as they may contain too much arsenic.)

FatMargarineButter, clarified butter or ghee, Dairy-free spread, Soya spread, Vegetable oils
CheeseCheese, Quark

Low lactose*: Edam, Gouda, Brie, Cheddar, Camembert, Blue cheese

Lactose-free: Soya cheese, rice cheese, almond cheese, cashew cheese

(*Important note: babies younger than 6 months shouldn't eat soft or unpasteurised cheeses)

YoghurtDairy yoghurt

Low-lactose: Cows' milk yogurt

Lactose-free: Soya, almond, coconut yogurt

CreamCream, Artificial cream, ice creamSoya cream, Oat cream
Food ingredientsLactose Lactoglobulin, Curd, Whey powder 

Other types of food may contain lactose, too – breakfast cereals being a good example. If your baby has lactose intolerance, be sure to check the ingredient list of any of the foods your baby eats to establish whether they’re suitable.

Will my baby grow out of a lactose intolerance?

Depending on the cause, your baby may fully recover from a lactose intolerance, or be able to tolerate more lactose in their diet in the future. For example, symptoms of secondary lactose intolerance if your baby has had gastroenteritis normally disappear within six to eight weeks4.  In most cases, lactose intolerance in babies is temporary.

If, on the advice of a medical professional, your baby has been following a lactose-free diet, it may be that your GP or paediatric dietician advises the reintroduction of lactose at some point. This is to test your baby’s reaction and see if there’s been any change. Be sure to keep in touch with your health professional and keep them in the loop about how your baby is getting on.

Next steps

  • If you suspect your baby has lactose intolerance, speak to your GP or health visitor. They will guide you in the next steps of identifying the issue and getting your baby back to full health.
  • You can also enter your baby's symptoms into our Baby Symptom Checker, which will give you practical advice and a handy symptom summary to discuss with your GP.

Your baby's future health begins here

At Aptaclub, we believe that experience helps to build resilience; and that each new encounter, whether in pregnancy or after birth, can shape your baby’s future development. With our scientific expertise and one-to-one round the clock support, we can help you and your baby embrace tomorrow.

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  1. NHS UK. Lactose intolerance [Online] 2023. Available at: [Accessed September 2023]
  2. NHS. What should I do if I think my baby is allergic or intolerant to cows’ milk? [online] 2022. Available at [Accessed September 2023] 
  3. NHS Inform. Lactose intolerance [online] 2023. Available at [Accessed September 2023]
  4. NHS Nottinghamshire Area Prescribing Committee. Guidance on the diagnosis and management of lactose intolerance [online] 2021. Available at [Accessed September 2023]
  5. NHS Cambridge University Hospitals. Milk allergy [online] 2023. Available at [Accessed September 2023]
  6. Heine RG, AlRefaee F, Bachina P, De Leon JC, Geng L, Gong S, Madrazo JA, Ngamphaiboon J, Ong C, Rogacion JM. Lactose intolerance and gastrointestinal cow's milk allergy in infants and children - common misconceptions revisited. World Allergy Organ J. 2017 Dec 12;10(1):41. doi: 10.1186/s40413-017-0173-0. PMID: 29270244; PMCID: PMC5726035.
  7. McCance. & Widdowson. (2002). The Composition of Foods. (6thed).
  8. Allergy UK. Lactose intolerance [online] 2023. Available at [Accessed September 2023] 

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