At what age babies can develop lactose intolerance? what are the symptoms.

A. Hello there ma'am please do not worry about it too much and lactose intolerance can come at any age and there are some symptoms which comes due to it are.. Pain and swelling in the tummy. Failure to settle at feeding times, coming on and off the breast. Failure to gain weight. Diarrhoea. Red bottom with skin worn away in places.. take care