But I do understand that a sauna feels nice.
I was able to reach Eric P. Widmaier, Hershel Raff, and Kevin T. Strang, through email. Is this claim substantiated by what is found in Vander’s Human Physiology? Maybe you would like to pause in your reading for suspense. OK. The answer is: No. They each told me that it is not. “We do discuss that sweat contains salt (sodium and chloride) that can represent a large loss of electrolytes with a large volume of sweat (e.g. exercising on a hot day),” Raff said. Very tiny amounts of lead, copper, and nickel do appear in sweat, but if you have dangerously high concentrations of these metals in your body it is probably best that you visit a hospital rather than an infrared sauna.
Our pal and Hairpin blogger Kelly Conaboy went to an infrared sauna for The Atlantic and guess what she found (besides a nice warm place to listen to Brian Eno)… Spoiler alert: the main thing your sweat contains is SALT.