Single Sauna Session Mobilizes White Blood Cells
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- Finnish researchers found that a single 30-minute sauna session paired with a short cold shower increased every type of circulating white blood cell, including neutrophils and lymphocytes.
- Neutrophil and lymphocyte counts returned to baseline within roughly 30 minutes after the sauna ended, which researcher Ilkka Heinonen said suggests immune cells are temporarily mobilized from tissue storage sites rather than persistently elevated.
- Ilkka Heinonen, an Academy Research Fellow at the University of Turku, compared the white blood cell release to what happens during physical exercise and said mobilized cells are better positioned to patrol the body for pathogens.
- Professor Jari Laukkanen of the University of Eastern Finland led the study of 51 adults with an average age of 50 and reported that individual cytokine responses correlated with how much each participant's body temperature rose during the session, even though average cytokine levels barely changed.
- The study, published in the journal Temperature, measured only the immediate effects of a single session, and the researchers cautioned the findings cannot establish whether repeated sauna bathing produces lasting immune changes.
Why it matters: For a field where regular sauna bathing has been linked to cardiovascular and metabolic benefits, this study offers a candidate mechanism — periodic flushing of white blood cells into circulation — that researchers can now test in longer trials. The 51-participant sample and single-session design mean the result is a mechanistic data point, not a prescription, but it gives clinicians a measurable immune variable to track in future sauna intervention studies.
