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Lactose intolerance in babies

5 mins


Lactose intolerance in babies is most common following an episode of infectious gastroenteritis when damage to the bowel lining results in a temporary deficiency in lactase – the enzyme which breaks down the lactose in milk. If a baby has gastroenteritis and passes uncommonly loose stools for more than 2 weeks, it could be a sign of temporary or transient lactose intolerance.

This article looks at the different types of lactose intolerance and advice to give to parents who are breast and/or bottle-feeding.

Mother holding her baby who is lactose intolerant

Signs of lactose intolerance in babies

Infants with lactose intolerance commonly present with one or more of the following symptoms:

  • Loose, watery stools
  • Abdominal bloating
  • Pain
  • Increased flatulence
  • Nappy rash

If a baby has gastroenteritis and passes uncommonly loose stools for more than 2 weeks, it could be a sign of lactose intolerance. If the diarrhoea resolves within 2 weeks of excluding lactose from the diet, a diagnosis of lactose intolerance can be made1.

Types of lactose intolerance in babies

Primary lactose intolerance is the most common cause of lactose intolerance worldwide with prevalence related to ethnicity2

Secondary lactose intolerance (also known as transient lactose intolerance) is common but a temporary cause of diarrhoea. It often occurs because of damage to the intestinal brush border – the site of lactase production.2

Congenital lactose intolerance is a rare condition where newborn babies produce very little or no lactase as a result of an inherited genetic fault that runs in families.2

Developmental lactose intolerance can be a problem with preterm babies born before the 34th week. Temporary lactose intolerance is due to immaturity of the small intestine. This usually improves as affected babies get older and their gut fully develops.2

Advice for parents with a lactose intolerant baby

  • For many, lactose intolerance in babies is temporary and will improve after a few weeks
  • If a mum is lactose intolerant, it is completely safe for her to breastfeed her baby2
  • Breastfed babies may benefit from lactase substitute drops
  • Lactose-free formula milks are available for formula-fed babies or lactase drops can be added to baby’s usual formula feed

Extra support: For parents

NHS Choices - Lactose intolerance. Accessed january 2019

Great Ormond Street Hospital. Lactose intolerance information. 2014

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  1. NHS. 2016. Lactose intolerance. Accessed january 2019.

  2. Heyman MB, Committee on Nutrition. Pediatrics 2006; 118: 1279–1286.