There are many reasons for the symptoms of dry mouth, which are not simply oral diseases, but also related to systemic diseases. 1, oral diseases: mumps, submandibular gland inflammation and other gland inflammation will cause too little saliva secretion, the elderly salivary gland atrophy, the function of the gland degeneration will cause dry mouth. In addition, the lack of vitamin B2, oral candida infection and some oral bad habits and often eat spicy food, periodontitis patients oral flora environment imbalance, poor oral hygiene will also cause dry mouth. 2, immune system diseases: the most common immune system disease that causes dry mouth is dry syndrome, mainly dry mouth, dry eyes, often also have salivary gland diseases and rheumatoid arthritis. 3, diabetes: diabetes is the most common disease causing dry mouth, early often manifested as dry mouth, thirst, and then develop more drinking, polyphagia, polyuria and wasting. 4, the lung does not distribute fluid, kidney yin deficiency: Chinese medicine believes that dry mouth is related to the lung, kidney, etc., need to take Chinese medicine to regulate. Once the symptoms of dry mouth appear, you need to go to the hospital for a specific examination to check the cause so that the treatment plan can be given accordingly.