Many people have the symptom of dry mouth at night, most of them are caused by the dryness and heat of the external environment and the serious lack of water in the body, so drinking water in time can solve the problem of dry mouth. If you often drink water at night or often dry mouth, and the phenomenon of dry mouth is very serious, it means that there are local diseases of the mouth or other systemic diseases. The local problem of oral cavity is mainly due to trauma or infection that causes damage to the function of salivary glands, so that saliva secretion is severely reduced, which results in the symptoms of extremely dry mouth, mostly seen in patients suffering from oral dryness syndrome. The disease mostly occurs in women aged 40-50 years old, due to immune dysfunction resulting in impaired salivary gland function, causing extreme dryness of the oral mucosa and a hot burning sensation in the mouth. There are two main types of other systemic diseases that can cause frequent dry mouth at night: 1. Diabetes mellitus, increased urine volume in diabetic patients, which reduces water in the body and causes dry mouth. 2. Patients with hyperthyroidism, due to increased sweating, can also cause dry mouth.