NPR begins a celebration of sweat — what it's made of, where it comes from and what it smells like. Spoiler alert: most of the time it doesn't have any smell at all.

Sweat is the body’s natural way of releasing heat. Water on your skin in the form of sweat evaporates, and through a process known as evaporative cooling, releases heat from your body.

There are many reasons why sweat may smell like ammonia, from diet to underlying health conditions. We explore the potential causes, treatments, and more.

This isn’t Gao’s first sweat sensor, either—previous variants also could detect the stress hormone cortisol, COVID-19, as well as a biomarker that indicates inflammation.

But, in fact, there is a stinky form of sweat. In addition to ecrine glands, Xu says there's something called apocrine glands. XU: They kind of exude a certain more protein-rich sweat.