Dry mouth may be caused by physiological factors such as drinking too little water and eating too much salt, or it may be due to dry syndrome, uremia, diabetes, etc. Dry mouth can occur. 1. Physiological factors: drinking too little water, eating too salty food, easy to cause dry mouth, sweat after strenuous exercise can appear after dry mouth, mental stress, anxiety can also appear dry mouth. 2. Dry syndrome: a diffuse connective tissue disease, mostly manifested as dry lips and mouth, some patients may also have dry eyes. 3. Uremia: generally due to the lack of antidiuretic hormone caused by renal tubular reabsorption of water obstacles, the emergence of polyuria, thirst symptoms. 4. Diabetes mellitus: mostly due to elevated blood glucose, causing osmotic diuretic effect is abnormal, and then appear polydrinking, polyuria, dry mouth and thirst symptoms. In addition, due to colds, rhinitis, sinusitis and other respiratory diseases due to poor nasal ventilation, open-mouth breathing and other factors caused by oral water evaporation and dry mouth; some patients in the taking of cold medicines, anti-allergy drugs can also appear dry mouth, if the persistent dry mouth, you should consult a doctor in a timely manner, a clear diagnosis of active treatment.