Sweating is an important bodily function that keeps you cool during hot weather and tough workouts. The end result is usually nothing more than sticky skin and the occasional pit-stained tee — but for a small percentage of people, sweating can also leave behind a blue toilet seat.
The phenomenon might be thanks to chromhidrosis, a rare skin condition marked by the production of colored sweat (think: blue, green, yellow, red, brown or black).