A little dry mouth may be caused by physiological factors, such as drinking too little water, excessive salt intake, etc. It may also be caused by pathologic factors, such as dryness, diabetes, and nasal diseases. 1. Physiological factors: (1) Drinking too little water: the amount of drinking water needed by the human body is about 1000 to 2000 ml per day, and if the amount of water intake is too little, dry mouth will occur. (2) Excessive salt intake: If the diet contains too much salt, dry mouth and thirst will also occur, mainly due to the sodium chloride content, which can easily increase the concentration of sodium in the body, thus causing an increase in plasma osmotic pressure, making people feel dry mouth and thirst. 2. Pathological factors: (1) Dry syndrome: an autoimmune disease, the patient’s secretory glands will be affected, such as parotid, lacrimal and salivary glands, etc., so there will be dry eyes, parotid gland enlargement and dry mouth and other symptoms. (2) Diabetes mellitus: It is mainly due to insufficient insulin secretion, which leads to the increase of blood glucose concentration and osmotic pressure in the blood, so that the water in the cells will be absorbed excessively, resulting in the symptoms of dry mouth. (3) Nasal diseases: such as chronic rhinitis, sinusitis and allergic rhinitis, etc., which can easily lead to hypertrophy of the adenoids in the nose, and the obstruction of nasal respiration, leading to open-mouth respiration, and so dry mouth is prone to occur. In addition to the above factors, mental thirst, chronic pharyngitis, etc. are also prone to the phenomenon of dry mouth, it is recommended to go to the neighborhood of the regular hospital checkups, to clarify the specific causes of the disease and then give treatment.