Congenital lactose intolerance (alactasia) is an extremely rare condition for babies to present with in the UK and would present within the first days of life with profuse watery stools (often mistaken for urine), dehydration and metabolic acidosis.
Babies who present in early life, with no history of infection preceding the problems, who have loose stools, gassiness and irritability are much more likely to have cow’s milk protein intolerance (CMPI) with secondary lactose intolerance.
For babies who are suspected as lactose intolerant, specialised lactose free (but cow’s milk protein based) formulas are available and are prescribable (Enfamil O‐ Lac or SMA Lactose free). If needed for more than 2 weeks an underlying cause (eg CMPI) should be sought. A ‘family history’ of lactose intolerance is irrelevant for the infant age group.
Please see right links for the latest guidance if you have a patient suspected lactose or milk- protein intolerance.