The causes of diarrhea caused by drinking milk on an empty stomach are: 1. Lack of lactase in the body, due to the lack of lactase in the human body, the lactose in milk can not be digested. Lactose in milk produces a lot of gas and acid under the action of intestinal bacteria, which stimulates intestinal contraction intestinal peristalsis to accelerate, resulting in bloating and diarrhea. It is recommended to eat solid foods such as bread, cookies and steamed buns before drinking milk, so that milk and food are fully mixed and increase the time milk stays in the stomach. 2, itself suffering from gastrointestinal tract diseases such as acute enteritis, gastrointestinal tract digestion and absorption function is weakened, resulting in absorption disorders caused by diarrhea. 3, because the proportion of water in milk is larger, drinking more milk on an empty stomach dilutes stomach acid, which is not conducive to digestion and absorption caused by Diarrhea. 4, the body itself has a cold or drink too much cold milk, can also lead to diarrhea, it is recommended that at this time should take warm milk orally.