The main cause of heavy breath is food residue and blood, which decays in the mouth through bacterial decomposition, and people with the following lifestyles and conditions are more likely to have heavy breath. One, poor oral hygiene, accumulated tartar can lead to periodontal disease, which leads to heavy breath. Second, insufficient saliva flow makes the mouth dry and thirsty, as saliva has the function of cleaning the mouth. Insufficient saliva flow, the necrotic cells in the mouth will gather in the tongue and decay and produce heavy breath. Third, poor denture hygiene, such as denture is not suitable, unhygienic, or sleep still wear will cause heavy breath. Fourth, smoking. Smoking can give off the stench of nicotine. Five, eating strong flavored food, such as onions, garlic, etc. can cause temporary heavy breath. Six, some diseases, such as sinusitis or liver problems, can sometimes cause unique bad breath.