Halitosis is a very common oral disease, the causes are mainly the following: 1, oral hygiene: do not brush teeth, do not rinse, or brush teeth sloppy people, food residues in the mouth long-term accumulation, fermentation and decomposition under the action of bacteria, the production of indole sulfur hydroxyl and amines and other substances, emitting a rotten stench. 2, oral diseases; decay in the decayed teeth, periodontal disease so that the gums are often in an inflammatory state, abscess bleeding, ulceration and pus, but also easy to produce a corrupt foul odor. 3, systemic diseases: some halitosis is caused by diseases in other parts of the body, such as indigestion, purulent bronchitis, lung abscess, etc., will be discharged through the respiratory tract odor, manifested as halitosis. In addition, diseases of neighboring organs, such as nasopharyngeal and nasal cavity diseases, septic maxillary sinusitis, etc., can also lead to bad breath. 4, special food fetishes: some people especially love to eat garlic, onions, etc., mouth, stomach will have an unpleasant smell. Prevention and treatment of halitosis, first of all, to develop good hygiene habits, timely removal of corrupt substances in the mouth can ensure oral cleanliness; secondly, to regularly conduct a comprehensive oral examination, especially oral diseases to be detected and treated in a timely manner, as long as the cause of halitosis is found, halitosis can be reduced or eliminated.