Sudden diarrhea in babies may be caused by acute gastroenteritis, indigestion, typhoid fever and other diseases. 1. Acute gastroenteritis: acute inflammation of the gastrointestinal mucosa that may be caused by improper diet, pathogenic microbial infections, etc. The baby may have diarrhea, abdominal pain, vomiting, loss of appetite and other symptoms. 2. Dyspepsia: a disease caused by gastric dysfunction, which may be related to improper diet and other reasons. Babies may have symptoms such as abdominal pain, diarrhea, and in severe cases, they may have diarrhea after eating. 3. Typhoid fever: mainly caused by typhoid bacillus, babies may have symptoms such as persistent fever, diarrhea and rose rash. Baby sudden diarrhea may also be caused by other reasons, parents are advised to bring their babies to the doctor in a timely manner, improve the relevant examination, targeted treatment.