Under normal circumstances, saliva from the salivary glands secretion outflow is sterile, has a clean mouth, dilute the role of odor, if the saliva has a bad smell may be periodontitis or other odontogenic diseases, as follows. 1. Periodontitis: periodontitis patients with periodontal pockets Porphyromonas gingivalis and Porphyromonas intermedia have elevated concentrations, these two bacteria have a certain odor-producing ability, which may lead to saliva odor. 2. Other odontogenic diseases: such as dental caries, food impaction, dry socket, blocked teeth, etc. can be due to the accumulation of bacteria and food residues lead to saliva odor. There may be other reasons for the odor of saliva, it is recommended to go to the hospital for medical treatment to identify the cause and then targeted treatment.