The common causes of diarrhea after meals include intestinal flora dysbiosis, acute gastroenteritis, irritable bowel syndrome and so on. 1. Intestinal flora dysbiosis: it is the dysregulation of the normal microecology of the intestinal tract, which is closely related to drug factors, dietary factors and abnormal intestinal dynamics. Its main manifestations are diarrhea, abdominal pain, abdominal distension, etc., and can be accompanied by nausea and vomiting. Therefore, people with intestinal flora dysbiosis can have diarrhea after meals, mostly seen in the elderly and infants. 2. Acute gastroenteritis: it is usually caused by unclean diet, cold abdomen, etc. It occurs mostly in summer and fall. Its main symptoms are abdominal pain, diarrhea, vomiting, dehydration and so on. So if you accidentally eat spoiled food, it is easy to induce acute gastroenteritis and diarrhea after meals. 3. Irritable Bowel Syndrome (IBS): It is a dynamic disease of the intestinal tract. If you eat allergic foods, spicy and irritating foods or emotional fluctuations, it is easy for IBS to occur, which manifests itself as postprandial bloating, diarrhea, and ringing in the abdomen. All in all, no matter which cause of postprandial diarrhea, it is recommended to go to the regular hospital for timely diagnosis and treatment.