Bad breath, or halitosis, is an unpleasant odor emitted when speaking or exhaling. Most cases originate in the mouth; a minority reflect nose, throat, lung, stomach or systemic problems. Because the nose quickly adapts to surrounding smells, many sufferers are unaware of their own odor, while nearby people notice it immediately. Recognising the origin guides targeted removal. Oral causes• Bacterial coating on the tongue: protein-rich debris trapped between filiform papillae is broken down into volatile sulphur compounds.• Gingivitis and periodontitis: pockets around teeth harbour anaerobic species that release malodorous gases.• Untreated caries, leaking crowns or impacted food: stagnant niches feed... Learn more