Milk flap is usually a sign of poor digestion and absorption, and is usually seen in the following situations: First, the most common is that the child has lactose intolerance, some children are born with lactase activity deficiency or decreased secretion of lactase, and usually have milk flap after birth. Second, the vast majority of secondary lactose intolerance, lactose activity caused by low lactose, lactose indigestion of food leads to increased milk flaps in the stool, usually seen after intestinal viral infections such as rotavirus enteritis, norovirus enteritis and so on easy to appear. Thirdly, the milk flap is also seen in children with obvious spleen and stomach function weakness, poor digestive function, can also be seen in the intestinal micro-ecosystem imbalance.