There are many reasons for low saliva, which can be divided into physiological factors and pathological factors. If it is pathological factors, you need to seek medical attention in a timely manner to clarify the specific causes, and then carry out the corresponding treatment. I. Physiological factors: mainly affected by age, environment, emotions, etc. 1. Age: as age increases, the secretion function of saliva gradually changes and the function of salivary glands decreases leading to a decrease in saliva secretion. Usually the amount of saliva of the elderly will be less than that of young people, which is a normal physiological change; 2, environment: if you drink too little water or in a dry or hot environment, it is easy to lead to dehydration, saliva secretion will also be reduced at this time, and patients will feel dry mouth; 3, emotions: if the patient has large emotional fluctuations, such as excessive sadness, tension, anxiety, worry is also likely to lead to a temporary reduction in saliva secretion. Pathological factors: mainly salivary gland diseases, menopausal syndrome, nutritional disorders and psycho-psychological factors. 1, salivary gland diseases: salivary gland damage caused by various factors can lead to reduced salivary secretion, such as chronic parotitis, submandibular gland duct stones, etc. The symptoms of dry syndrome also include salivary gland function decline and reduced saliva secretion. 2, menopausal syndrome: mainly due to the human body It can indirectly lead to the decrease of saliva, which is common in menopausal women; 3, nutritional disorders: such as vitamin deficiency, which can easily cause dry mouth and less saliva; 4, mental and psychological factors: it can be seen in neurasthenia and anxiety disorders, in which there are also patients who show increased saliva secretion. In addition, radiation therapy, chemotherapy or hyperthermia, taking diuretics and after major surgery also tend to cause dry mouth.