Every type of white blood cell measured rose immediately afterward. Researchers counted white blood cell subtypes and measured 37 cytokines, the signaling proteins immune cells use to coordinate. The results "may indicate that sauna bathing mobilizes additional white blood cells into the bloodstream from tissues," he said, with the cells later redeposited. Circulating white blood cell counts rise for many reasons unrelated to improved defense, including stress, dehydration, and simple postural changes. That a single 30-minute sauna session at 73 degrees Celsius temporarily increased all measured types of circulating white blood cells in 51 middle-aged adults.