This is a state that is not related to whether or not you drink water. The cause of dry mouth is usually due to certain medications and radiation treatments or diseases caused by aging. Dry mouth manifests itself when the salivary glands in the mouth do not have enough saliva to keep the mouth moist. Many medications, including many over-the-counter medications, can produce dry mouth as a side effect, such as histamines and medications for depression, and patients on these medications experience dry mouth after use, and the more water they drink, the more dry mouth they experience. Some chemotherapy treatments for cancer patients can change the composition of saliva and the amount of saliva produced, but the dry mouth phenomenon is temporary and will recover after the treatment is completed, but some chemotherapy treatments for the head and neck can damage the salivary glands and lead to a decrease in saliva production. When the salivary glands are completely destroyed, permanent dry mouth can occur and the symptoms cannot be recovered. Many seniors experience dry mouth as they age, which can be caused by medications or long-term health conditions. Diabetes is the most common disease, and some people may have immune disorders that cause dry mouth syndrome, which can occur more severely. Ageing can also lead to a decrease in the secretion function of the oral salivary glands and atrophy of the oral mucosa, both of which together can also lead to dry mouth discomfort. The main reason for dry mouth is in some medications or some treatments, etc. When dry mouth occurs, we should find the cause and solve the disease problem in time.