Sudden diarrhea in a 2-year-old baby may be due to non-infectious factors (such as improper feeding, etc.) or infectious factors (such as viral infection, bacterial infection, etc.). 1. Non-infectious factors: (1) improper feeding: mostly seen in artificial feeding, if the 2-year-old baby feeding irregularly, feeding too much, too early to give a lot of fatty or starchy food, etc., can cause sudden diarrhea. (2) climatic factors: if the weather suddenly becomes cold, so that the 2-year-old baby’s abdomen is cold, can make the intestinal peristalsis increase, thus diarrhea. 2. Infectious factors: (1) viral infections: such as rotavirus, viruses invade the intestinal tract of 2-year-old babies, which can impair the ability of the mucosa of the small intestine to absorb water and electrolytes, thus leading to a large amount of intestinal fluids in the intestinal lumen, triggering sudden diarrhea. (2) bacterial infection: such as Escherichia coli, Vibrio cholerae, etc., bacteria invade the intestinal tract of 2-year-old babies, will produce enterotoxin, thus triggering sudden diarrhea. 2-year-old baby sudden diarrhea, there may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.