The mouth is always dry does not necessarily suffer from diseases, such as breathing through the mouth, etc., but cannot exclude the factors of disease, such as dry syndrome, diabetes, etc.. 1. Breathing through the mouth: breathing through the mouth air is directly inhaled into the airway, easy to stimulate the oral mucosa, which can easily lead to bacteria, viruses into the body, may appear pharyngitis, dry mouth and other symptoms. 2. Dry syndrome: due to autoimmune deficiency caused by dry syndrome, resulting in the parotid gland is affected, thus reducing the secretion of saliva, there will be a dry tongue, dry mouth, swallowing difficulties, etc., usually pay attention to drink more water, maintain oral hygiene, etc., to effectively alleviate the symptoms. 3. Diabetes: Due to genetic factors, bad habits and other factors that lead to the occurrence of diabetes, thirst, dry mouth, easy to fatigue and other symptoms, it is recommended to eat a reasonable diet, appropriate exercise, etc., to alleviate the symptoms. If the symptoms are not relieved in time, it is recommended to go to the hospital for examination and treatment.