Health conditions

Lactose intolerance in babies

  • Lactose intolerance is the reduced ability to digest milk sugars, due to insufficient amounts of the gut enzyme called lactase.
  • Breastfed babies can be lactose intolerant, because lactose is found in breast milk as well as baby formula.
  • Diarrhoea can be a symptom of lactose intolerance in babies.
What causes lactose intolerance?

Lactose intolerance occurs when the lining of the intestine (bowel and gut) has been damaged. This damage is commonly caused by diarrhoea infected with viruses, such as the rotavirus.

Babies with lactose intolerance cannot digest lactose properly and it remains indigestible in the intestine. The build up of lactose attracts water which produces watery faeces (poo) causing diarrhoea.

Very young babies often are not yet producing enough of the enzyme (lactase) which helps to digest lactose. Your baby may have lactose intolerance without ever having had infectious diarrhoea, but the enzyme will increase with age, so there is no need to stop breastfeeding unless the lactose intolerance is severe, causing dehydration or poor growth.

It is preferable to continue breastfeeding if you are able, but if your doctor advises you to stop breastfeeding it is usually only for a very short time, so you will need to take steps to keep up your milk supply.

What are the signs and symptoms?

Symptoms may include:

  • pain and swelling in the tummy
  • failure to settle at feeding times, coming on and off the breast
  • failure to gain weight
  • diarrhoea
  • bulky, frothy and watery faeces
  • red bottom with skin worn away in places
  • passing wind and crying when passing faeces
  • irritability.
How is lactose intolerance diagnosed?

If your baby has had rotavirus or another type of infectious diarrhoea the recurrence may indicate your baby has lactose intolerance.

If you think your baby is lactose intolerant, see your doctor.

How is lactose intolerance treated?

Your baby could try lactose-free formula for 1 to 4 weeks and then graded back on to breast milk or a standard infant formula once there have been no symptoms for a week and the bottom has healed.

If your baby is old enough to eat solids it is important they don’t eat food high in milk content, such as yoghurt, soft cheese and custard. Cheddar and other hard cheeses are okay. A baby should not have juice, cordial or other sweetened drinks.


Regrading is the process of reintroducing your baby’s normal feeding cycle.

Your baby may take between 5 and 7 days to regrade to their normal feeding cycle. Sometimes a doctor or a nurse may advise you to regrade in a shorter period of time. When regrading is complete, foods containing milk can be reintroduced.

Regrading guide for young babies

Replace one bottle of lactose-free formula with one breastfeed or bottle of usual infant formula each day for 5 days, until all lactose-free bottles have been replaced by usual feeds, as shown below. If your baby develops diarrhoea, go back one step. If it persists see your doctor.

Day one:

  • 1 x breastfeed or usual formula
  • 4 x lactose-free formula.

Day two:

  • 2 x breastfeed or usual formula
  • 3 x lactose-free formula.

Day three:

  • 3 x breastfeed or usual formula
  • 2 x lactose-free formula.

Day four:

  • 4 x breastfeed or usual formula
  • 1 x lactose-free formula.

Day five:

  • Back to usual feeding.

Where to get help

  • See your doctor.
  • Speak to a child health nurse.
  • Ring healthdirect on 1800 022 222.


Perth Children's Hospital (PCH)

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

Link to HealthyWA Facebook page