There are many reasons for bad breath, mainly including the following aspects: 1, the cause of bad breath is mainly oral hygiene and oral diseases, if you do not pay attention to brushing and rinsing, food debris will be left in the teeth, or oral crevices, too long food debris will emit a stench to produce bad breath. 2, oral diseases caused by, such as gingivitis, dental damage is the main cause of bad breath, the main reason. 3, you must carefully brush your teeth, pay attention to rinse after meals. Usually must carefully brush your teeth, pay attention to rinse your mouth after meals. 3, there is a stomach disease is also the main reason for bad breath, if the stomach fire is too large, stomach function is weakened, eat into the food can not be digested in a timely manner, it will be fermented to produce odor, emanating from the mouth is bad breath.