Authoritative research has found that bad breath is caused by volatile sulfide (VSC) produced by anaerobic bacteria decomposing sulfur-containing protein in oral cavity. Sulfur-bearing protein comes from the dung reef in the intestine. Protein containing sulfur will be continuously released from the dung reef in the intestine, and these protein will spread to the oral cavity, which will be decomposed by anaerobic bacteria in the oral cavity to produce volatile sulfide (VSC), which will be released from the back of the tongue and throat, thus forming bad breath. Remarks: Sulfide (VSC) is a volatile gas with unpleasant smell and disgusting taste.

Dung reef is the root of bad breath.