Healthy people’s mouth smells fresh. Smoking, drinking alcohol, drinking coffee and often eat onions, garlic, leeks and other spicy food, or addicted to stinky tofu, rotten eggs and other smelly food, also prone to oral odor, which is also normal. When the mouth often or persistent odor, it should be noted whether the signs of disease. What causes can cause odor in the cavity? 1, mouth and nose inflammation due to bacterial decomposition, especially anaerobic bacteria, its decomposition produced sulfide, etc., and produce bad breath. Such as dental caries, gingivitis, periodontitis, oral mucositis, sinusitis, etc. 2, H. pylori infection in addition to peptic ulcer, chronic gastritis and other diseases, but also often cause bad breath. Chronic cholecystitis, chronic pancreatitis, chronic hepatitis, chronic gastritis and other chronic diseases of the digestive tract are often accompanied by bad breath. Long-term constipation, the body can produce harmful substances can not be discharged in a timely manner, is absorbed into the blood and cause bad breath. 3, the whistling tract diseases such as bronchitis, bronchiectasis, lung abscess, tuberculosis, etc., may also cause bad breath. 4, excessive psychological pressure, dieting and weight loss, or due to illness can not eat, the elderly, menstruating women saliva secretion is reduced, oral tissue resistance is reduced, easy to infect germs and thus produce bad breath. 5, drugs can also cause oral odor antispasmodic painkillers, diuretics, Chinese medicine with warming effect of Chinese medicine with warming effect of Chinese medicine to reduce saliva secretion appears bad breath; taking hypoglycemic drugs such as sulfonylureas, phenibut, etc., antibacterial drugs such as metronidazole, tinidazole, tetracycline, anti-inflammatory analgesics, etc. can appear pharmacogenic oral metallic taste; clindamycin, clarithromycin, zopiclone appear bitter mouth is common. In addition, there is still a case of psychogenic halitosis, mostly seen in young people in the workplace who are very concerned about their image. Doctors and others cannot smell the odor either, but the patient insists that he or she smells bad breath, often with varying degrees of anxiety and obsessive-compulsive tendencies.