Five-month-old babies usually spit up because of physiological reasons such as improper feeding, immature digestive system and other diseases such as acute gastroenteritis and pneumonia. 1. Physiological reasons: five-month-old babies may spit up after eating milk if they eat too fast or eat too much milk, as well as cry before eating milk and other situations. The five-month-old baby’s gastrointestinal development is not perfect, the stomach is horizontal, and the entrance is more relaxed, the milk will reflux out. 2. Pathological reasons: clinically, some diseases can also lead to 5-month-old babies spit up, such as the baby ate unclean food can lead to the occurrence of acute gastroenteritis, can appear spit up, crying and other manifestations. Some babies after the occurrence of pneumonia its clinical manifestations are often atypical, can appear spitting milk choking, spitting bubbles, shortness of breath, lips purple and other manifestations. If a five-month-old baby spits up seriously, or choking, spitting bubbles, shortness of breath, cyanosis of the lips and other manifestations, it is recommended to go to the hospital in a timely manner.