Bad breath in the elderly may be physiological factors, but also may be the manifestation of certain diseases, such as oral systemic diseases, systemic diseases, etc., should be timely consultation to identify the cause of the disease. 1. Physiological factors: excessive hunger or eat certain stimulating foods, such as garlic. It may also be caused by smoking. This part of bad breath is transient and can be regulated by improving daily life style. 2. Pathologic factors: (1) Diseases of the oral system, due to older age, oral diseases for a longer period of time, poor hygiene in the mouth, tartar is more, the neck of the teeth attached to food debris, soft scale, plaque, the use of bacterial decomposition will produce foul-smelling gas and bad breath. (2) systemic diseases, such as respiratory diseases or digestive diseases, because the elderly may often have systemic diseases, if there is inflammation of the respiratory tract or digestive diseases, may produce foul-smelling gases, through the respiratory tract, digestive tract or blood circulation, reached the oral cavity, the formation of halitosis. If the elderly have bad breath, it is recommended to go to the stomatology department of the regular hospital for examination as soon as possible, and appropriate treatment according to the cause of the disease.