Methanethiol (also known as methyl mercaptan) is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood and brain of humans and other animal as well as plant tissues. It is disposed of through animal feces. It occurs naturally in certain foods, such as some nuts and cheese. It is also one of the main chemicals responsible for bad breath and the smell of flatus. The chemical formula for methanethiol is CH3SH; it is classified as a thiol. It is sometimes abbreviated as MeSH.