Patients with bad breath first choose dentistry for examination, followed by respiratory and gastroenterology for consultation and treatment. Patients with bad breath first consider whether it is related to inadequate personal hygiene and cleaning, such as improper brushing, untimely brushing, and over-eating high protein diet or smoking and drinking, etc. If bad breath is caused by these conditions, it can be relieved after removing the causative factors, and there is generally no need to consult a doctor. If after self-adjustment still can not relieve bad breath, consider and pathological factors related to different diseases choose the department there are some differences, as follows: 1, oral lesions: oral disease patients are prone to halitosis, common periodontitis, dental caries, pericoronitis, etc., the affected area of food residues and necrotic tissue by bacterial decomposition, may appear unpleasant odor, it is recommended to visit the stomatology department for treatment; 2, Respiratory lesions: Some patients may also suffer from lung abscess, pulmonary hemorrhage, atrophic rhinitis, etc., resulting in fishy and unpleasant odor in the mouth and causing halitosis, which can be diagnosed differently by visiting the respiratory department. Usually the primary lesion is treated first, then with the corresponding oral care; 3, digestive system lesions: some patients have esophageal, gastric, duodenal lesions, etc., which may lead to the retention of food in the intestinal tract, by bacterial decomposition or fermentation to produce odor, coupled with bleeding and ulcers at the lesion site, can cause patients to exhale unpleasant taste from the mouth, usually accompanied by digestive system symptoms such as abdominal pain, bloating, loss of appetite, etc., should go to the gastroenterology department for targeted treatment. The patient should go to the gastroenterology department for targeted treatment. When patients have bad breath, they should pay attention to oral hygiene, brush their teeth in the morning and evening, rinse their mouth after meals, which can effectively reduce bad breath, avoid over-eating before going to bed, and choose a suitable toothpaste or breath freshener, which can also briefly relieve the symptoms of bad breath. If bad breath is not relieved or other accompanying symptoms appear, you should actively go to the hospital for treatment to avoid affecting the quality of life.