When a patient has diarrhea as soon as he drinks water, consider the following causes: 1. What is considered is that the patient has irritable bowel syndrome, which can be caused by food stimulation, environmental stimulation, and emotional stimulation. 2. What is considered is that the water itself is not clean and the water hygiene in the area is not up to standard. For example, raw water that is not boiled and water that is infected by parasites, or water that is infected by bacteria, may lead to diarrhea. 3, what is considered is that the water is colder and causes stimulation to the human gastrointestinal tract, which can cause increased gastrointestinal peristalsis and therefore produce diarrhea. 4, the patient himself has enteritis, which, combined with drinking unclean water, can lead to increased inflammation causing diarrhea. 5, what is considered is that the patient has an imbalance of intestinal flora. The microorganisms contained in the drinking water that are not up to the standard of hygiene are excessive, which can aggravate the imbalance of flora in the intestine.