Bad breath is an abnormal taste or odor in the mouth that is usually detectable by yourself and can also be smelled by others around you. Bad breath is more common, can occur at any age, can be a long-term presence, but also can be a temporary problem. There are many causes of bad breath: 1, bad breath caused by eating: including eating garlic, onion, leek, etc., which can be eliminated in a short time. 2, untreated caries, in the cavity often accumulate food residue, due to the bacterial growth, the corruption and decomposition of the odor. Timely repair of cavities can eliminate bad breath. 3, periodontitis patients, periodontal pockets are septic inflammation, saliva in the mouth mixed with pus, also make the mouth has bad odor. 4, with fixed dentures, real teeth and dentures contact area is not easy to brush clean, the accumulation of food in this, corruption and odor. In this regard, try to set movable dentures, easy to clean, will also reduce bad breath. 5, respiratory diseases, chronic sinusitis, rhinitis, necrotizing granuloma, pharyngitis, tonsillitis. Nasal tumors, bronchitis, bronchial carcinoma, etc., can also cause bad breath. 6, systemic diseases, such as diabetic ketosis patients with rotten apple odor in the mouth; liver patients exhale ammonia odor; acute rheumatic fever patients with sweet and sour taste in the mouth; uremia or renal failure patients exhale ammonia and urine gas; lung abscess or bronchial dilatation patients exhale corrosive foul odor; aplastic anemia, granulocyte deficiency, leukopenia, thrombocytopenia can cause infection in the mouth and produce bad breath. In short, the treatment of halitosis, the first thing to diagnose clearly, remove the cause of the disease can be cured.