Self-assessment of bad breath methods are: gas test, cotton swabs dipped in the mucous membrane test, oral examination of the gums whether bleeding, the existence of digestive system diseases, etc. 1. hold up both hands over the mouth in front of 1-2cm, ha out of the gas such as the presence of odor to prove the existence of bad breath. 2. Dip a cotton swab into a small amount of oral mucosal tissue and place it in the nostrils to smell whether there is a foul odor. 3. Check whether there is bleeding gums in the oral cavity, bleeding when brushing teeth and gums with redness and swelling can also cause bad breath, and local bacterial corrosion after the occurrence of dental caries in the oral cavity can also cause the presence of bad breath. If there is dyspepsia and the above mentioned problem of bad breath, you need to exclude the problem of Helicobacter pylori infection of bad breath occurs.