Some people often tend to confuse dry mouth and dry eye syndrome, in fact, they are not exactly the same thing. Dry mouth syndrome is very common, and according to statistics, about 30% to 50% of middle-aged and elderly people suffer from different degrees of dry mouth syndrome. Strictly speaking, dry mouth is a symptom caused by multiple factors rather than an independent disease, but behind this symptom, some organic diseases are often concealed. If the degree of dry mouth is more severe and lasts for a long time, it is likely to be a local manifestation of some systemic diseases, and it is worth to be alert. The causes of dry mouth are mainly physiological and pathological: such as the elderly salivary glands due to age atrophy, saliva secretion is reduced, coupled with the reduction of the nervous system response, oral mucosa dryness and loss of elasticity and dry mouth symptoms; In addition, some people sleep with their mouths open, with the nose and mouth breathing at the same time, so that the water in the mouth evaporates, so after waking up often feel dry mouth, which is physiologically caused by dry mouth. The influence of mental factors on dry mouth should not be ignored: such as emotional changes, psychological imbalance, long-term anxiety, tension and fear, especially depression can cause dry mouth. There is also damage and atrophy of salivary gland alveoli after radiation treatment of head and facial tumors; or lack of saliva in the mouth after surgical removal of salivary glands; as well as taking antidepressants, painkillers, antihypertensive drugs, diuretics, anti-allergy drugs and anti-tumor drugs, etc., which can cause a decrease in saliva secretion and dry mouth. Pathological dry mouth: for example, diabetes mellitus is caused by increased plasma osmolality and polyuria due to elevated blood sugar; uremia is caused by increased urine volume and urination, and the body loses a lot of water and dry mouth; hyperthyroidism is caused by excessive sweating and excessive water loss and dry mouth; dry syndrome patients can show obvious dry mouth due to epidemic inflammation that destroys salivary glands, lacrimal glands and glands in the mucous membrane of nasal cavity, resulting in reduced saliva secretion. These are pathological dry mouth. Dry eye is the common name of keratoconjunctival dryness or dry keratoconjunctivitis, which is also a multifactorial disease. It is a type of disease that causes eye discomfort due to tear film instability and eye surface damage caused by abnormalities in the quantity or quality of tears from any cause. The common symptoms are dryness and foreign body sensation in the eye, and other symptoms include burning sensation, photophobia, redness and pain, blurred vision and easy fatigue, and mucous filiform discharge. However, the symptoms vary greatly among individuals. There are many causes of dry eye, such as prolonged computer operation or game playing, or long-distance car driving, and a reduced number of blinks, which can cause a decrease in tears. Surveys have confirmed that 90% of people who work in front of a computer for more than 3 hours a day suffer from dry eye. There is also a decrease in tears or a decrease in quality caused by wearing contact lenses, suffering from allergic conjunctivitis, and other reasons such as atmospheric pollution and ultraviolet light. In addition, taking some antihypertensive medications and some psychostimulants can also have an effect on tear production. Clinically, dry eye is generally classified into 2 types: partial tear production deficiency and evaporation overload, but they often cross over and rarely occur separately. Among them, the partially insufficient tear production type is mostly seen in patients with dry syndrome. Dry syndrome is a kind of systemic, chronic inflammatory autoimmune disease mainly invading the exocrine glands, and it is common in middle-aged and old-aged women. Dry mouth and eyes are important clinical symptoms of dry syndrome. Due to the destruction of salivary and lacrimal glands caused by immune inflammatory lesions, the secretion of saliva and tears is reduced, which can be manifested as obvious dry mouth (the incidence is about 70-80%) and dry eyes. In severe cases of salivary deficiency, it is necessary to drink frequently, and it is difficult to eat solid food, often complicated by dental caries, oral candidiasis and infections; in the case of tear deficiency, there is no need to cry, vision is reduced, and it can be complicated not only by intraocular infections, but also by corneal ulceration, perforation or permanent blindness. These symptoms often plague patients so much that many of them gradually become depressed and their quality of life decreases significantly. In addition, the multisystem damage caused by this disease is often an important reason for the poor prognosis of this disease. Therefore, dry mouth and dry eyes can occur independently or be localized manifestations of certain systemic diseases. Dry mouth and dry eyes are not the same thing as dry syndrome. If you suspect pathological dry mouth and dry eye caused by certain diseases, you should promptly go to a regular large hospital for a clear diagnosis, active treatment and control the progress of the disease.