A new Finnish study found that sitting in a sauna can push more white‑blood cells into your blood for a short time. These cells act like tiny soldiers that look for germs and help keep you healthy.
During a 30‑minute sauna visit, participants took a quick cold‑shower break halfway through. After the heat, the number of every kind of white‑blood cell rose.
About half an hour after leaving the sauna, the levels of neutrophils and lymphocytes – two key immune cells – went back to normal.
"The heat seems to free extra white‑blood cells from their storage spots in the body and send them into the bloodstream," explains Ilkka Heinonen, a researcher at the University of Turku. "When they are in the blood, they can move around faster and spot threats more easily."
Exercise does something similar. By moving more immune cells around, both sauna and workout may improve the body’s ability to watch for and fight infections.
Cytokine Shifts Linked to Body Heat
The team also measured cytokines – tiny messengers that direct immune actions. Overall, sauna use caused only small changes in average cytokine levels.
However, people whose body temperature rose more during the session showed bigger cytokine changes. The rise in temperature did not affect white‑blood‑cell counts in the same way, says study leader Professor Jari Laukkanen from the University of Eastern Finland.
Long‑Term Benefits Still Unknown
Regular sauna use has been tied to many health advantages, but this research only looked at the immediate impact of a single session. We still don’t know if repeated sauna visits create lasting improvements in immune function.
The study involved 51 adults with an average age of 50. Results were published in the journal Temperature, which focuses on how the body controls heat.