Cetylpyridinium chloride (CPC) is a cationic quaternary ammonium compound in some types of mouthwashes, toothpastes, lozenges, throat sprays, anti-sore throat sprays, breath sprays, and nasal sprays. It is an antiseptic that kills bacteria and other microorganisms. It has been shown to be effective in preventing dental plaque and reducing gingivitis. It has also been used as an ingredient in certain pesticides. However, this ingredient has also been alleged (according to WebMD, eMedicine,) to cause brown stains between the teeth similar to Chlorhexidine rinse. Flossing your teeth regularly and with good technique will prevent this type of extrinsic staining.[Sōrs rīkwest]