My kids sweat plenty in this hot heat, but they don't smell afterward. I on the other hand need all kinds of deodorant. Why doesn't kid sweat smell?
There are two types of sweat glands: (1) eccrine sweat glands and (2) apocrine sweat glands.
- Eccrine sweat glands are present from birth in humans and secrete sweat that is mostly water and functions in evaporative cooling.
- Apocrine sweat glands are found in the armpits and groin regions and become active in humans at puberty (although the distribution appears to be broader fetally). These sweat glands secrete an oily substance containing lipids and proteins that through interactions with bacteria on the skin (e.g., bacteria digesting lipids), lead to the "smelliness" of adults (including body odor).
So it's not really the sweat that smells, it's the action of bacteria on apocrine sweat that becomes prevalent after puberty.