Where Bad Breath Comes From Most, but not all, bad breath comes from bacterial plaque and food accumulated mainly towards the back of the tongue. The problem is, there are all sorts of not-likely-but-possible other reasons for halitosis: upset stomach, anxiety, inflamed gums, saliva deficiency, infections and removable dentures are among them. What Not To Do Because nobody—but nobody!— wants bad breath, a billion-dollar industry has sprung up hawking a variety [...]