Lactose intolerance

Food allergies and food intolerances are not the same and it is essential to understand how to distinguish between the two conditions

A food allergy is an adverse reaction to the protein component of a food, which evokes an immunological response. An intolerance is an adverse reaction to a ‘non protein’ component in the food, which does not involve the immune system.

Lactose intolerance is caused by a reduced level of the enzyme lactase, which breaks down the lactose in milk so that it can be absorbed into the blood.

Congenital deficiency (when the baby is born without the lactase enzyme) is extremely rare, whilst primary deficiency (caused by an inherited genetic trait that results in a decline in lactase production) does not typically occur before two years of age.

Secondary lactose intolerance is the most common cause of deficiency in younger infants and is a temporary problem that normally occurs after a bout of gastroenteritis. It is also thought to be a possible cause of colic.

Secondary lactose intolerance is the most common cause of deficiency in younger infants


  • Bloated stomach, possibly with abdominal pain
  • Wind
  • Loose stools or diarrhoea
  • Mild colic
  • Poor weight gain or even weight loss.

Formula milks

Once lactose intolerance has been diagnosed, babies may be recommended a lactose-free formula (e.g. Aptamil Lactose Free or SMA LF Lactose Free Formula). These are nutritionally complete milks that can be used from birth for infants who have a congenital or temporary lactase deficiency, or for a period of six to eight weeks for infants suffering with secondary lactose intolerance. These milks taste similar to routine infant formula milk, so babies should not notice a difference.

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