What causes bad breath? Is it due to an unhealthy stomach?

Halitosis refers to an unpleasant odor emanating from the mouth during breathing, and its causes are varied, including but not limited to gastrointestinal issues. On one hand, gastrointestinal diseases such as gastritis and gastric ulcers can indeed cause halitosis. These conditions lead to weakened intestinal motility, prolonging the retention time of food in the stomach and thereby producing odorous gases, which may travel through the digestive tract to the mouth, resulting in bad breath. On the other hand, halitosis may also be caused by increased oral bacterial load, oral diseases such as periodontitis and dental caries, medication-induced dry mouth, environmental factors like smoking and insufficient water intake, and lifestyle habits such as consuming strongly flavored foods. Therefore, halitosis is not always caused by poor stomach health; it may also result from a combination of multiple factors. If halitosis occurs, it is recommended to comprehensively consider possible contributing factors and take appropriate measures to address and improve the condition.