Although dry mouth is not a discrete condition, it is a discomfort that has plagued many people, especially the elderly, for long periods of time or at one time or another. Severe dry mouth can cause difficulty in tongue rotation, affecting speech communication and eating. The following conditions can cause dry mouth: 1, diabetic patients can have dry mouth and thirst due to increased plasma osmolality and polyuria caused by elevated blood sugar; 2, patients with rhinitis, sinusitis and nasal septum distortion can have dry mouth due to poor nasal ventilation and evaporation of water from the mouth due to open-mouth breathing; 3, asthma patients can have dry mouth due to accelerated and deepened breathing and excessive evaporation of water from the respiratory tract; 4, patients with sleep apnea have dry mouth at night due to open-mouth breathing. Open-mouth breathing causes dry mouth in the morning; 5, menopausal people can be too nervous, anxiety, etc. caused by dry mouth; 6, some pituitary tumor patients can also appear dry mouth; 8, dry mouth in patients with dry mouth syndrome. This disease is mainly because some factors destroy the main salivary glands in the mouth such as parotid, submandibular and sublingual glands, and also inhibit the secretion of lacrimal glands and glands in the mucous membrane of the nasal cavity, thus causing unbearable dry mouth, dry eyes and dry nasal cavity, and it is difficult to turn the tongue and close the eyes when it is serious. Dry mouth is not the same as thirst. Thirst is mostly seen after drinking too little water, eating too much salty or dry food, after strenuous exercise and after heavy sweating. This kind of thirst caused by too little water or too much water loss can be relieved by replenishing water; however, it is difficult to work for dry mouth caused by various diseases, and often increases the burden on the kidneys due to excessive water consumption, which is inappropriate for the elderly and people with poor kidney function. Therefore, we remind everyone that when dry mouth cannot be relieved within a short period of time after supplemental drinking, you should go to the hospital for a comprehensive examination in order to make a clear diagnosis and carry out effective treatment.