Hi David , Hydrogen Peroxide can be an effective mouth wash,it is a strong oxizing agent that kills bacteria very readily. Saliva should not affect hydrogen peroxideat all. In fact saliva contains hydogen peroxide as part of a defense mechanism. This defense mechanism is called the lactoperoxidase system. The system consists of the enzyme lactoperxidase, thiocyanate and hydrogen peroxide which kill bacteria. (1) Hydrogen peroxide would be an effective mouth wash, but since it is a strong oxidizing agent, the Agency for Toxic Substances and Disease Registry reported that a 3% solution of hydrogen peroxide may cause skin and mucous membrane irritation.(2) Thanks for asking Larry (1) Brock.T et al Microbiology with Applications p.184 (2) www.atsdr.cdc.gov/atsdrhome.html