Milk with watermelon may cause diarrhea. It may be related to factors such as chilling, lactose intolerance and weak gastrointestinal function. 1. Cold: If ice milk and ice watermelon are eaten together and eaten too cold, the abdomen may appear to be cold, coupled with the fact that both milk and watermelon contain a lot of water, diarrhea symptoms will usually occur. 2. Lactose intolerance: Some people may have lactose intolerance. Milk contains a lot of lactose, and when you drink milk and eat watermelon, diarrhea often occurs. 3. Weak gastrointestinal function: Some people may have weak gastrointestinal function, poor digestion and absorption. When you drink milk and eat watermelon, if you can’t digest and absorb it in time, and it may stimulate the mucous membrane of the gastrointestinal tract, you may experience diarrhea. Milk and watermelon will eat diarrhea may have other reasons, please go to the hospital in time, complete the examination to clarify the cause, under the guidance of the doctor to give targeted treatment or treatment.