Diarrhea the day after drinking alcohol may be caused by acute gastroenteritis after drinking alcohol and getting cold, or it may be caused by the patient’s allergy to alcohol, or it may be caused by irritable bowel syndrome. 1. Acute gastroenteritis: If the patient suffers from acute gastroenteritis after drinking alcohol, it can lead to diarrhea the next day after drinking alcohol, and the patient can also have nausea, vomiting, abdominal pain, fever and other symptoms. 2. Alcohol allergy: If the patient is allergic to alcohol, diarrhea and abdominal pain may occur the day after drinking alcohol. 3. Irritable bowel syndrome: If the patient has irritable bowel syndrome, it can also lead to diarrhea the day after drinking alcohol, and the patient can also have abdominal pain, bloating, nausea, anxiety and other symptoms. In addition to the above reasons, other factors can also lead to symptoms of diarrhea the day after drinking alcohol, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to find out the cause of the problem and ask the doctor to deal with it.