Bad breath should first be checked for oral diseases, and at the same time rule out the digestive and respiratory system diseases. Some anaerobic and microaerobic bacteria in the oral cavity can cause disease, but there are also non-pathogenic bacteria, some belong to the pigment class bacilli, all produce bad breath. Treatment according to the cause; bad breath in the mouth, such as dental caries, periodontal disease must go to dentistry treatment, followed by the removal of plaque and tartar on the surface of the teeth, turn to doctors to clean teeth (scaling), the best twice a year cleaning treatment. In addition, brush your teeth carefully is an important measure to maintain oral hygiene. Brush your teeth twice a day. Before going to bed at night, brush carefully and finely. Brushing can reduce oral microorganisms by about 60%. Carefully rinse the mouth can eliminate the smell of food residue, the water in the mouth, squeeze the water with the tongue, gargle with cheeks, rinse a few more times to get rid of the smell, such as still have food smell, can be a few green tea leaves in the mouth chew and then rinse, chlorophyll in tea can get rid of odor. Periodontal disease must be treated by a doctor, periodontitis is inflammation of the tissue around the teeth and pus, alveolar bone resorption, teeth and gums form pockets, bacteria in the periodontal pockets multiplying bacteria, general brushing and rinsing no therapeutic effect, under the treatment of doctors can remove these bacteria to achieve anti-inflammatory purposes.