Diarrhea from drinking plain milk may be caused by drinking frozen milk, milk spoilage, lactose intolerance or protein allergy, etc., as follows: 1. If the milk drunk is frozen in the refrigerator, the frozen milk will cause irritation to the stomach, especially drinking frozen milk on an empty stomach will cause abdominal pain and diarrhea. 2. If the milk has expired, the milk has deteriorated, and drinking spoiled milk will cause The company’s main business is to provide a wide range of products and services to its customers. But some people will be allergic to proteins, and after drinking milk the body will react to these proteins, which will stimulate the intestines and enhance their peristalsis, resulting in diarrhea.