There are three reasons for beer diarrhea: 1. Beer itself is hypertonic, and if the amount of alcohol consumed is relatively high, the hypertonic fluid in the intestine reaches a certain level within a short period of time, which can easily lead to an increase in osmotic pressure, causing an increase in vascular permeability, leading to diarrhea, which is relatively common. 2. Beer contains a small amount of ethanol, and for this alcoholic content is relatively high, it is easy to stimulate the intestinal mucosa, causing congestion and edema of the intestinal mucosa, leading to diarrhea. 3. 3. Patients with chronic intestinal disorders and digestive malfunctions are prone to intestinal disorders when drinking alcohol, causing an increase in the number of diarrhea, and even abdominal pain, nausea, vomiting and other symptoms of digestive malfunctions. Therefore, drinking beer with diarrhea is one of the most common manifestations of dyspepsia and should be avoided if possible or a colonoscopy should be perfected to assist in the diagnosis.