A 30-minute sauna briefly surged white blood cells into the bloodstream
The full story behind my Short: Finnish study (51 adults): every circulating white-cell type measured rose after one 30-min sauna with a mid-session cold shower; neutrophils and lymphocytes were back to normal within 30 minutes. Temperature 2026.
One session, short-lived counts — does not prove lasting immunity. Combined with a cold shower. This page is not medical advice. Ask your doctor before using a sauna if you have heart or blood-pressure issues.
The short version
Researchers in Finland found that a single 30-minute sauna session, with a brief cold shower halfway through, temporarily increased every type of circulating white blood cell they measured in 51 adults (average age 50) [1][2].
What they found
Ilkka Heinonen (University of Turku) and colleagues suggest sauna heat mobilises immune cells from tissue stores into blood for short-term patrol (immune surveillance), then they redeposit — timing similar to the temporary rise seen with exercise [1]. Cytokine averages changed little overall, though some tracked how much body temperature rose [1].
Limits and caveats
- Immediate effects only. No proof of lasting immune improvement or fewer infections [1].
- Cold shower included. Results reflect the combined routine, not heat alone [1].
- Not medical advice. Sauna can be risky with heart or blood-pressure problems — ask a doctor.
Watch the Short
Why it matters
Regular sauna use has been linked to health benefits in other studies. This acute immune-cell surge is one more clue about what heat exposure does in the short term — not a prescription.
Full narration (transcript)
A single 30-minute sauna sent every white blood cell type they measured surging into the bloodstream. Finnish researchers studied 51 adults, average age 50. The session included a brief cold shower halfway through. Neutrophils and lymphocytes rose — then, within 30 minutes afterwards, those counts were back to normal. Lead voices include Ilkka Heinonen at the University of Turku and Jari Laukkanen at Eastern Finland. They think heat mobilises immune cells from tissues into blood, so they can patrol — then they settle again. It's a short burst, a bit like the temporary immune-cell rise seen with exercise. But this doesn't prove it improves lasting immunity or cuts infection risk. It was one session only. And because of the cold shower, it's the combined routine, not heat alone. Published in the journal Temperature. This isn't medical advice. Check with your doctor before using a sauna if you have heart or blood-pressure issues. Follow the link to the main website for much deeper information.
Sources
- [1] ScienceDaily, 28 Oct 2026 (University of Eastern Finland materials). https://www.sciencedaily.com/releases/2026/10/261027231021.htm
- [2] Heinonen IHA, Laukkanen JA et al. Acute Finnish sauna heat exposure… Temperature. 2026;13(2):186. doi:10.1080/23328940.2026.2645467. https://doi.org/10.1080/23328940.2026.2645467
Credits
Images via Wikimedia Commons (illustrative unless stated): Traditional Finnish sauna healing.jpg (Ville Kurki, CC BY-SA 4.0); Wood stove of smoke sauna of Kuusijärvi, Kuninkaanmäki, Vantaa, Finland, 2023 April.jpg (Ximonic (Simo Räsänen), CC BY-SA 4.0); WBC (neutrophil) at centre, numerous erythrocytes and platelets (dot like bodies) in Wright's stained peripheral blood smear (PBS) microscopy.jpg (Ajay Kumar Chaurasiya, CC BY-SA 4.0); Neutrophil 1.jpg (Dr. Roshan Nasimudeen, CC BY-SA 3.0); Red White Blood cells.jpg (Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick), Public domain); Blood pressure cuff.jpg (Sistema d’Emergències Mèdiques (SEM), CC BY-SA 3.0 igo). On-screen graphics: own.
AI voice note: the narration in the Short is an AI clone of my own voice (Chatterbox TTS by Resemble AI, MIT licence), used with my consent. I wrote the script and checked the figures against the sources above.
This page is general information, not medical or dental advice. Please talk to a doctor, dentist or pharmacist about your own health.