The causes of diarrhea in newborns are non-infectious and infectious. Non-infectious causes include: 1) allergies, including allergy to milk proteins; 2) digestive enzyme deficiencies, with lactase deficiencies being more common; 3) inflammatory bowel disease, with an inflammatory response in the intestine, chronic diarrhea, very high C-reactive protein, and ineffective antibiotic therapy; and 4) medication factors. Infectious causes include bacterial as well as viral infections. Bacteria are more common with Escherichia coli, the source of infection mostly comes from diarrhea before and after delivery of the pregnant mother or the presence of Escherichia coli in the cervix, viral infections mainly include rotavirus or other coxsackieviruses, etc.