Suggestion: Hello, I'm glad to answer your question. The main causes of halitosis and bitterness are the weakening of gastrointestinal function and abnormal food fermentation, which leads to the prolonged residence time of food in gastrointestinal tract. Other causes include gingivitis and pharyngitis (which can cause dry mouth). Generally speaking, it is recommended to go to the hospital for dental examination first. If it is caused by gingivitis or pharyngitis, the symptoms of bad breath will naturally disappear. If the gastrointestinal motility is weakened, there are the following methods: firstly, pay attention to increasing exercise (if necessary, take gastrointestinal motility drugs such as motilium or cisapride orally), increase gastrointestinal peristalsis, promote gastrointestinal emptying, and shorten the residence time of food in the gastrointestinal tract. At the same time, pay attention to increase the intake of cellulose-rich foods such as celery and bananas, eat less greasy and indigestible foods, and pay attention to increase exercise to promote gastrointestinal peristalsis. But it is suggested that if the gastrointestinal function is weak due to diseases such as chronic gastritis.