Dry mouth is characterized by subjective thirst and the desire to drink water, and the symptoms improve slightly after drinking, but soon the thirst starts again. It is important to pay attention to dry mouth caused by stomatitis, diabetes, etc. According to Chinese medicine, dry mouth and thirst are mostly caused by deficiency of liver and kidney yin, and the fluid does not go on the carrier, or caused by heat and fluid injury and decoction of fluid. Cause 1: The lack of water in the body causes thirst. People feel thirsty when the weather is hot, doing heavy physical labor, blood loss, burns, vomiting, diarrhea, and sweating a lot due to high temperature (heat stroke). Cause 2: Thirst caused by diabetes. One of the roles of hormones is to coordinate the metabolism of water and salt in the human body. Once the balance of this hormone is disrupted, it can cause frequent thirst. Cause 3: Thirst caused by brain injury. Some people also get thirsty after brain injury or neurosurgery.