Underarm odor is caused by the interaction of bacteria and the secretions of what glands?
Apocrine sweat glands.
There are two main types of sweat glands:
- eccrine glands: occur over the entire body that open directly onto the skin surface.
- apocrine glands: these open in hair follicles and are found in hairy areas such as the armpit.
Eccrine glands secrete sweat that is composed mainly of water and salts, this is not very interesting for bacteria. In contrast, the apocrine glands secrete sweat that is composed mainly of fatty substances (cholesterol, fatty acids, glycerol, wax esters, squalene etc.) but also contains a protein with a sugar group (glycoprotein) called sialomucin. This sialomycin is what bacteria love.
The apocrine sweat is odorless untill bacteria start to break the molecules down. Different bacteria have different ways of breaking it down. The byproducts cause the smell and can differ from person to person, because everyone has different bacteria on their skin.