Stuck in this week's brutal heat wave? You may be surprised to learn that sweat doesn't actually smell—and NPR has posted a video from the chemistry podcast Distillations to explain why. Turns out that there are two types of sweat glands, eccrine and apocrine; the former covers the body and produces sweat that keeps us cool, while the latter exists only in "certain" areas—the armpits and crotch—and that's where the olfactory trouble begins.
Apocrine makes sweat with extra proteins, some of which are connected to smelly odorant molecules. That combo still doesn't smell, but bacteria in our stinky regions are hungry for those proteins. So bacteria break that connection, eat the proteins, and release the smell that drifts up to our nose. So next time you're stuck in an elevator with Mr. Stinky, know that it's just his bacteria making you yearn for the doors to open.