Dry mouth can be caused by insufficient water intake, tongue infection, hyperthyroidism or dry syndrome. 1. Insufficient drinking water: the water content of the human body can account for about 60% to 70% of the human body, if you often eat spicy, high salt food or long-term exercise, but less water, may lead to dehydration, which can cause the symptoms of dry mouth. 2. Tongue inflammation: If patients suffer from tongue inflammation, there may be symptoms such as tongue papilla atrophy, peeling, redness, swelling, erosion, etc., and these symptoms may cause the mouth to feel dry. 3. Hyperthyroidism: If the concentration of thyroxine is high in patients with hyperthyroidism, it may promote energy metabolism and increase heat production, which may lead to dry mouth. 4. Dry syndrome: patients with dry syndrome may lead to dry oral mucosa, saliva, and will destroy the period of oral salivary glands, can not produce a normal amount of saliva, resulting in patients with dry mouth symptoms. If the patient has a dry mouth, it is recommended to go to the relevant department of a specialized hospital in a timely manner to clarify the cause, and if it is a disease factor, it should be treated in accordance with the doctor’s instructions actively.