Lactose in milk has been implicated in infant colic and feeding problems, with a migration to lactose-free formulas.
However, Lactose is very important in the infants diet as it adds flavour to milk, aids absorption of calcium and promotes the growth of probiotics. Growing infants need lactose as a carbohydrate source. Did you know there is more lactose in breast milk than cow’s milk (but no one suggests stopping breast feeding as a treatment for lactose intolerance). Lactose intolerance is actually very rare in infants and only develops in older children and adults of Afro-Asian descent. Infants can develop a temporary lactose intolerance if they get viral gastroenteritis, but this rapidly settles in a week or two.
Source: British Society for Allergy and Clinical Immunology Congress. Telford UK, Sept 2015