Foamy baby poop is usually caused by indigestion, partly caused by lactose intolerance and so on. 1. Indigestion: If your baby eats food that is not easily digested and absorbed, it may cause your baby’s digestive burden to increase. Indigestion will usually occur, which will lead to foamy stools. 2. Lactose intolerance: Lactose intolerance may be present if the baby is unable to obtain enough lactase. Lactose intolerance may result in diarrhea, abdominal cramps, bloating, farting and other symptoms after breastfeeding, as well as foamy poop. If your baby has foamy poop, go to the hospital immediately to identify the cause of the problem under the guidance of your doctor and then follow up with treatment.