The fact that babies spit up after eating milk may be due to physiological phenomena, or congenital megacolon, lactose intolerance and other diseases. 1. Physiological phenomenon: babies spit up after eating milk is mostly considered to be caused by the vomiting center is not yet well developed, or the stomach capacity is small, the lower esophageal sphincter relaxation reasons. If the breastfeeding speed is too fast and the amount of breastfeeding is too much, it can also cause spitting up after breastfeeding, which is a normal physiological phenomenon. 2. Congenital megacolon: this disease is the result of polygenic inheritance, abnormal embryonic development and abnormal intestinal microenvironment, common symptoms include persistent constipation, vomiting, abdominal distension, etc., and some of the affected children will spit up after eating milk. 3. Lactose intolerance: the occurrence of this disease may be related to congenital lactase gene reduction, or pathogenic microbial infections, inflammatory bowel disease and other acquired factors, the main symptoms are abdominal distension, diarrhea, vomiting, back to the milk, etc., and sometimes can be manifested as spitting up after eating milk. There may be other reasons for babies to spit up after eating milk, so it is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.