1. Reasons for green poop in babies 1.1 Immature baby digestion The baby\’s digestion is not fully developed, and the flora in the intestine is also unstable, which will cause the food to be unable to be fully digested and absorbed, resulting in the discharge of green poop. 1.2 Milk powder allergy or lactose intolerance Some babies may be allergic to certain ingredients in milk powder or lactose intolerant, resulting in intestinal irritation and lactose intolerance.