Lactose Intolerance in Babies

Lactose Intolerance is a serious issue in young babies, as it can lead to chronic diarrhoea which can ultimately cause dehydration.

Which infants are more likely to be lactose intolerant?

It is normal for the amount of the enzyme lactase to decline after a baby has been weaned. The amount and speed by which this decline occurs depends on the cultural and ethnic background of the infant. It has been found that infants of Asian or African descent are more likely to be affected than those of European descent. This is probably due to genetic traits and the huge part milk and other such dairy products have in the western diet; the continual consumption of lactose containing products stimulates lactase activity.

With the increasing survival rates of babies born prematurely we are seeing another reason for infant lactose intolerance. Lactase levels only increase during the third trimester of pregnancy. So, any babies born before this stage have a marked decrease in lactase levels compared to those babies carried to term. Such premature babies have insufficient amounts of lactase and are unable to digest the lactose found in breast milk and/or infant formula.

Suggestions have been made that infants who were purely breast-fed are less likely to develop lactose intolerance. Breast milk contains a higher lactose content than most commercially available infant formulas, so you would expect breast milk to be a trigger of lactose intolerance, but appears this is not the case. But this is does not exclude breast-fed infants from developing lactose intolerance. This could happen if infants have low-fat feeds. This occurs when the infant don’t feed effectively and means they are less likely to get the fattier hind milk, this causes the milk to be digest emptying causing too much lactose for the small intestine to digest at once.

If feeding is the problem, rather than the infants lack of lactase then an assessment of feeding should be made. Improving feeding technique usually resolves the problem.

To summarise, the following are possible reasons for lactose intolerance in infants:

  • Genetic traits
  • Cultural background
  • Premature birth
  • Low-fat feeds


The following are noticeable symptoms of lactose intolerance in infants:

  • Diarrhoea
  • Unsettled
  • Crying
  • Restless sleep
  • Stomach ache
  • Flatulence – “a windy baby”
  • Vomiting
  • Acidic breath
  • Dehydration
  • Weight loss

Diagnosing a lactose intolerant infant

To diagnose a lactose intolerant infant a full history should be taken to include; feeding patterns and bowel habits. A physical examination should look for signs of dehydration (a tell tale sign of lactose intolerance). All baseline observations should be taken in order to track the babies progress, these should include: pulse rate, blood pressure, respiration rate and details on the babies growth and development. Often lactose intolerant infants thrive poorly due to the malnutrition and dehydration caused by the lactose intolerance.

If the infant is severely unwell a stool acid test should be taken to clarify if lactose intolerance is the problem. A stool of less than pH 5.5 is usually indicative of lactose intolerance. If the test is negative another condition is the likely cause and further tests should be carried out.


It is distressing for parents to see their infant so acutely unwell, but lactose intolerance can be managed and controlled once admitted to hospital. The key to treating the infant is restoring the balance unset by the undigested lactose in the infant’s digestive system. To restore this balance rehydration and control of the electrolyte imbalance are essential.  This is normally achieved by a rehydration solution.


If your baby is lactose intolerant they may still be able to manage small quantities of breast milk without any unpleasant side effects. If this is not the case, and can’t manage any breast milk you should refer to your doctor. They can prescribe infant formula, specially designed for lactose intolerant babies. These formulas are lactose-free soy formulas. Your doctor should also give you advice on other substitutes for dairy foods so your child doesn’t miss out on any essential nutrients.

It may be suggested to use lactase drops, which digest the lactose in the cow’s milk before it is consumed so it can be consumed without any side effects.

The following is a list of different ways to feed your infant instead to avoid lactose containing milk:

  • Soya milk
  • Breast milk with lactase added to it
  • Partially hydrolysed infant formula
  • Extensively hydrolysed infant formula

You should also note that the amount of lactose found in breast milk is independent to the amount of lactose consumed by the mother.

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