There are many causes of oral odor: 1, the body’s internal organs, gastrointestinal function, endocrine, body metabolism and immunity damage caused by bad breath, such as Helicobacter pylori infection and dry syndrome, and may appear in addition to bad breath multiple symptoms. 2, oral diseases cause bad breath, such as tooth decay, gingivitis, periodontitis, etc.. This bad breath is the most direct and easiest to treat bad breath. 3, constipation halitosis, also belongs to the body metabolic factors, constipation of many women, persistent stool will make the intestinal tract blockage, the accumulation of toxins in the body, will produce a certain bad breath. 4, psychological factors, bad emotions lead to bad breath, generally ignored, but clinically confirmed that psychological factors may also be one of the causes of bad breath. 5, dietary habits lead to bad breath, belongs to the oral class factors, long-term eating onions and garlic, salty and fishy food, do not pay attention to oral hygiene is also prone to habitual halitosis. 6, rhinitis can lead to bad breath, when people suffer from various rhinitis diseases, nasal secretions backward into the nasopharynx, that is, the “nasal leakage” phenomenon, causing nasopharyngitis syndrome, which affects the breath. 7, smoking causes bad breath, tobacco nicotine and other harmful substances will affect the normal blood circulation of the body, so that the local immunity is reduced, and eventually lead to bad breath and other physical ailments. Smoking is also a variety of oral diseases (including periodontitis, gingivitis, oral mucositis, etc.) triggering factors, thus causing bad breath. 8, diabetes causes bad breath, diabetes makes endocrine disorders, reducing the amount of insulin secretion, carbohydrates are difficult to break down, causing active fat metabolism, which produces acetone components, and then through the lungs, discharged by the mouth and nasal cavity, this gas is what we call bad breath. Treatment of bad breath: Active treatment of the primary disease, adjustment of diet and a healthy lifestyle.