Heat, infrared and the body's response
Wet heat versus dry sauna
A dry sauna heats air to roughly 70 to 100 °C at low humidity, so sweat evaporates and cools you. A steam sauna runs far cooler but close to saturated, so sweat cannot evaporate. They are two different ways of taking heat.
Also called steam bath versus dry sauna, moist heat, Finnish sauna
Dry sauna. Finnish-style sauna is hot, dry air, usually 70 to 100 °C at 10 to 20 per cent relative humidity, with the whole body including the head inside. Sweat evaporates freely, which is the body’s main cooling route, so a very high air temperature is tolerable.
Wet heat. A steam sauna runs at a much lower temperature but near saturation. Sweat pours rather than evaporates, so the cooling route is largely closed and heat also arrives by condensation. Our saunas are head-out, so the airway stays in room air.
Why the skin behaves differently. The research on our steam studies page is about moist heat hydrating and softening the lipids of the stratum corneum, the skin’s outer layer. Dry heat dries the skin surface instead.
Why it matters here
Most of the sauna research people have read about is Finnish dry sauna. A head-out steam sauna is a different exposure, which is worth knowing when you weigh what you have read against what you are looking at.