Bad breath is a topic of general interest. In this study, the treatment for bad breath in traditional Chinese medicine was reviewed with a special focus on pathologic diagnosis and crude drug prescriptions. It was shown that bad breath developed based on both systemic and local diseases. Some systemic conditions, including nasal, paranasal, pulmonary and digestive diseases, are considered to cause bad breath. The morbid state of a patient with bad breath has been recognized as being based on "heat syndrome" and "Qi-stagnation syndrome." Bad breath based on "heat syndrome" is manifested as thirst and ulceration of the oral cavity, and has been treated with crude drugs such as Coptis rhizome, Scutellaria root and gypsum. One case study reported that bad breath resulting from a dry mouth was treated with byakkokaninjinto, a Kampo formulation containing gypsum. "Qi" is considered to be the vital energy of all life forms including for the functioning of organs and mental and emotional activity. "Qi-stagnation syndrom," referring to the dysfunction of organs, is manifested as psychosomatic symptoms such as irritability, a flushed face and restlessness. Bad breath based on "Qi-stagnation syndrome" has been treated with crude drugs such as Cnidium rhizome, clove and cinnamon bark. Modern dental and medical treatment both accept the participation of psychogenic agents in the development of bad breath. Bad breath also develops based on periodontal and oral diseases. This type of bad breath has been treated with mouth-wash (collutorium) containing Asiasarum root, Angelica dahurica root and Cnidium rhizome. This historical evidence regarding crude drug prescriptions contributes to the development of mouth care products for preventing and treating bad breath.