Bad breath, also known as halitosis, is a symptom in which a noticeably unpleasant breath odour is present.It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive compulsive disorder.

The concerns of bad breath may be divided into genuine and non-genuine cases. Of those who have genuine bad breath, about 85% of cases come from inside the mouth The remaining cases are believed to be due to disorders in the nose, sinuses, throat, lungs, esophagus, or stomach. Rarely, bad breath can be due to an underlying medical condition such as liver failure or ketoacidosis. Non-genuine cases occur when someone feels they have bad breath but someone else cannot detect it. This is estimated to make up between 5% and 72% of cases.