What causes bad breath?

Bad breath (halitosis) causes considerable inconvenience and embarrassment in daily life. As is well known, every disease has its underlying cause—and halitosis is no exception. Research has shown that numerous factors can trigger halitosis, significantly affecting individuals’ social interactions. So, what exactly causes bad breath?

What Causes Bad Breath?

Smoking, alcohol consumption, coffee drinking, and frequent intake of pungent, spicy foods—such as onions, garlic, and leeks—or preferences for strongly odorous foods like stinky tofu and century eggs—all predispose individuals to halitosis. In adolescent girls, unstable ovarian hormone secretion may contribute to halitosis, as ovarian function is closely linked to oral mucosal health. Hormonal imbalances disrupt normal mucosal functions—including antimicrobial activity and self-cleansing capacity—thereby weakening the mouth’s natural defenses, causing dryness, and ultimately leading to halitosis. Insufficient food intake can also cause halitosis. For instance, individuals undergoing calorie-restricted diets or those unable to eat due to illness experience reduced salivary flow, creating an environment favorable for anaerobic bacterial growth—and consequently, halitosis.

Maintaining good oral hygiene is essential, as halitosis is primarily caused by gingivitis, periodontitis, gingival bleeding, heavy dental calculus buildup, or accumulated debris. A high concentration of bacteria in interdental spaces may likewise produce halitosis. Patients are advised to brush thoroughly and rinse after meals—especially upon waking—and to schedule regular professional dental cleanings at a dental clinic; these measures play a crucial role in alleviating halitosis. Improving gastrointestinal function is equally important: poor digestion may cause undigested food to linger in the gastrointestinal tract, allowing acidic reflux into the oral cavity and resulting in halitosis. In such cases, treating the underlying gastric disorder first will typically lead to corresponding improvement in halitosis symptoms.

Patients are encouraged to consume more high-fiber foods, vegetables, and fruits, which help promote digestion. Moderate physical activity can also enhance gastrointestinal motility and improve digestive efficiency. We hope this information proves helpful to you.