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In a study of 51 adults, a 30-minute sauna session with a brief cold shower halfway through was followed by increases in every type of circulating white blood cell the researchers measured. Neutrophil and lymphocyte counts returned to their starting levels within 30 minutes; the study did not test whether sauna use improves long-term immunity or prevents illness.
A study of 51 adults found that a single 30-minute sauna session, interrupted by a brief cold shower, was followed by a temporary rise in every type of circulating white blood cell the researchers measured. The changes had subsided for neutrophils and lymphocytes within 30 minutes after the session, and the findings do not establish that sauna bathing strengthens immunity over time or lowers the risk of illness.
The research, reported by ScienceDaily and published in the journal Temperature, measured participants’ blood cells around one sauna-and-cooling session. Researchers observed increases in circulating neutrophils and lymphocytes, as well as the other white blood cell types included in their measurements. Neutrophils are among the cells that can respond early to infection; lymphocytes include cells involved in recognizing specific threats and coordinating immune responses.
The authors suggest the rise may reflect immune cells moving from tissue storage sites into the bloodstream, then returning to tissues afterward. That explanation is a proposed interpretation of the observed changes, not evidence that cells detected or fought an infection during the experiment. The reported return of neutrophil and lymphocyte counts to their original levels within 30 minutes after the session points to a short-lived change in circulation.
The team also examined cytokines, proteins that help immune cells communicate. Average cytokine levels changed little overall, but some cytokine levels varied in relation to how much participants’ body temperature rose. White blood cell counts showed no similar association with temperature change, according to the report. The distinction suggests that cell counts and signaling molecules did not respond in the same measured way.
What a Short-Term Cell Rise Shows
The results offer a snapshot of how the body responds to a sauna routine, rather than evidence of a lasting health outcome. A temporary increase in cells circulating through the blood is relevant to immune surveillance, the movement of immune cells through the body as they monitor for potential threats. But the study did not show that this brief shift makes participants less likely to become ill or changes their ability to recover from infection.
The pattern resembles one response seen during exercise, which can also temporarily alter the number of immune cells in circulation. That comparison helps frame the finding as a possible short-term physiological response; it does not mean sauna bathing and exercise have identical effects or benefits. For readers weighing sauna use as a health practice, the key distinction is between a measured change in blood counts and a proven improvement in health.
Because the blood cell rise was temporary, the study cannot establish whether repeated sessions produce different effects, whether any changes persist with regular use, or whether the response varies in people with different health conditions. The report adds biological detail to research on sauna bathing but leaves those practical questions open.
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The Sauna Routine Tested
The report describes a study involving 51 adults with an average age of 50. Participants completed one 30-minute sauna session that included a brief cold shower halfway through. Researchers assessed immediate changes in circulating white blood cells and cytokines, rather than tracking infections, illness rates, or long-term immune health.
The cooling break matters when interpreting the results: the experiment tested a combined sauna-and-cold-shower routine, so it cannot isolate the effect of heat alone. The findings were published in Temperature, a journal focused on body temperature regulation and its effects on human physiology. Earlier research has associated regular sauna bathing with potential health benefits, but this particular experiment addresses an immediate response to one session, not those longer-term claims.
“This may indicate that sauna bathing mobilizes additional white blood cells into the bloodstream from tissues, where they are then redeposited after the session.”
— Ilkka Heinonen, Academy Research Fellow at the University of Turku
Long-Term Immune Effects Unanswered
The study measured the immediate response to one session; it does not establish whether repeated sauna use leads to lasting changes in immune function or fewer infections. The reported account also does not provide enough detail to determine how the response might differ by health status, sauna habits, or other participant characteristics. Since the routine included a cold shower, the separate effects of heat and cooling remain unclear. The proposed movement of cells between tissues and blood is an interpretation, and the reported measurements do not show that the cells encountered or neutralized pathogens.
Questions for Further Studies
Further research would need to examine repeated sessions and longer follow-up to test whether these short-lived changes have any lasting biological or health significance. Studies comparing sauna heat alone with routines that include cooling could help identify which part of the session is associated with the observed response. Until such evidence is available, the finding is best understood as an immediate change in circulating cell counts, not proof that sauna bathing prevents illness or improves immunity over time.
Key Questions
Did one sauna session raise white blood cell counts?
In this study, researchers observed increases in every type of circulating white blood cell they measured after one 30-minute sauna session with a brief cold shower. The report does not establish that the change improves health or prevents illness.
How long did the measured increase last?
The report says neutrophil and lymphocyte counts had returned to their starting levels within 30 minutes after the session. It does not describe a lasting increase.
Was the effect caused by sauna heat alone?
That is not clear. Participants had a brief cold shower during the session, so the findings reflect the combined routine rather than heat in isolation.
Does this prove sauna use prevents infections?
No. The study examined immediate changes in blood cells and cytokines, not infection rates or long-term immune outcomes. It does not show that sauna bathing prevents illness.
Source: sciencedaily.com
