The main causes of bad breath are digestive system diseases and oral diseases. If bad breath occurs, the first choice is to consult the gastroenterology department, such as patients with symptoms of indigestion, poor diet, overeating, overeating, especially too much at night, such cases can appear bad breath. For dry stools or diarrhea, you also need to register with the gastroenterology department. If it is caused by food stagnation, you can give the treatment of eliminating food and guiding stagnation, commonly used are Baohe Wan and Hovenia Guiding Pill. If it is caused by stomach fire, for example, the patient usually likes to eat spicy food, thirsty after meals, dry mouth and drink, including dry stools, toothache, mouth and tongue sores, this situation can be considered as a large stomach fire. The patient can be given drugs to clear the stomach and fire, such as Huanglian Qingzhi Pills and Huanglian Jiehu Tang, which can be applied. A common disease in gastroenterology is H. pylori infection. If there are H. pylori patients in the family, or if there is a family history of stomach cancer, it is recommended to monitor H. pylori. So when patients visit the clinic, they can have a carbon 13 or carbon 14 breath test, and if they have H. pylori infection, they can choose the standard four-company regimen of proton pump inhibitor plus bismuth plus two antibiotics for a 14-day course of treatment, and standardized treatment can eradicate H. pylori. Oral diseases can also cause bad breath, such as periodontitis, gingivitis, dental caries, etc. It is recommended to visit dentistry. Therefore, patients with bad breath should first distinguish whether it is a digestive system disease or an oral disease, and should choose different departments for consultation, and treat the cause of the disease with symptomatic treatment for better results.