Lactose intolerance: Some babies have a particularly high number of stools after breastfeeding, and the stools are also relatively thin. But the baby’s growth and development is not affected by anything, and all kinds of laboratory tests are normal. This is related to the development of the baby’s intestinal tract and is a lack of lactase. What should I do if I am lactose intolerant? After the addition of complementary foods at six months, the stool will be formed and no special treatment is needed. Adding lactase can also help.