Sebum, which comes from the Latin word for "fat," is an odorless oil produced by the sebaceous glands. The substance contributes to oily hair and skin, while overproduction of sebum can cause acne. As sebum breaks down, the bacteria gives off an unpleasant smell, which can contribute to body odor.
Sebum isn't all bad, though: It's also what coats your hair to make it nice and shiny.
