Clinically, there are more reasons for less saliva, which are divided into physiological factors and pathological factors. Physiological factors: mainly affected by age, environment, emotion, etc. 1, age: with the increase of age, the secretion function of saliva gradually change, the function of salivary glands decline to reduce 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, the environment: if you drink too little water or in a dry, hot environment, it is easy to lead to body dehydration, at this time, the saliva secretion will also be reduced, the patient will feel dry mouth; 3, emotions: if the patient’s mood fluctuations, such as excessive sadness, nervousness, anxiety, and so on, it is easy to lead to a temporary reduction in saliva secretion. Pathological factors: salivary gland diseases, menopausal syndrome, nutritional disorders and psychosomatic factors. 1, salivary gland diseases: salivary gland damage caused by a variety of factors, there will be a decrease in salivary secretion phenomenon, such as chronic parotiditis, submandibular gland ductal calculi, etc.. Symptoms of dry syndrome also include a decline in the function of the salivary glands, secretion of saliva is reduced; 2, menopausal syndrome: mainly due to the body’s estrogen level decreased significantly caused by the saliva can indirectly lead to a reduction in the common menopausal women; 3, nutritional disorders: such as vitamin deficiencies, prone to cause a dry mouth, less saliva; 4, psychosomatic factors: can be seen in the neurasthenia, anxiety, etc., which also has part of the Patients show increased salivary secretion. In addition, radiotherapy, chemotherapy, hyperthermia, diuretics and major surgery, also easy to cause dry mouth.