Finnish Study Reveals Sauna Bathing Mobilizes Immune Cells for Enhanced Pathogen Patrol

A Finnish study shows a 30-minute sauna session mobilizes immune cells into the bloodstream, enhancing the body's ability to patrol for pathogens.

By: AXL Media

Published: Apr 9, 2026, 11:12 AM EDT

Source: Information for this report was sourced from the University of Eastern Finland (UEF Viestintä).

The Mobilization of the Immune "Patrol"

Researchers in Finland, a nation synonymous with sauna culture, have provided new evidence on how heat exposure affects human biology. The study, published in the journal Temperature, demonstrates that a standard sauna session—30 minutes of heat with a brief cold-shower break—mobilizes white blood cells from tissue storage into the bloodstream. This periodic release is considered highly beneficial for immune surveillance, as it allows white blood cells to reach various parts of the body more efficiently to identify and respond to potential diseases or pathogens.

Temporary Surge in Defense Cells

The increase in white blood cell counts was observed across all categories, with a particular emphasis on neutrophils and lymphocytes, which are the primary responders in the body's immune defense system. Interestingly, these counts returned to baseline levels within 30 minutes of exiting the sauna. Ilkka Heinonen, an Academy Research Fellow at the University of Turku, explained that this suggests the cells are not "created" by the heat, but rather redeposited into tissues after their brief patrol. This temporary "boost" is similar to the physiological response triggered by moderate to high-intensity physical exercise.

Cytokines and Body Temperature Correlation

In addition to cellular counts, the research team measured cytokine levels—the chemical messengers that mediate immune responses. While the average cytokine levels remained largely stable, the researchers noted a specific correlation: the higher an individual's core body temperature rose, the more certain cytokine levels fluctuated. Professor Jari Laukkanen, who led the study at the University of Eastern Finland, highlighted that this temperature-dependent response was unique to cytokines and was not observed in the mobilization of white blood cells.