Sauna and the immune system: Can heat protect you from illness?
The winter months often bring sniffles, coughs and unwanted sick days. But what if you could strengthen your immune system just by sitting in a warm room? Research suggests that regular sauna use, especially when combined with cold therapy, can be an effective weapon against seasonal viruses.
In this article we look at the science behind the sauna’s effect on the immune system, and how heat can help your body defend itself.
The most important things to know
- A single sauna visit temporarily increases the number of white blood cells in the blood.
- Regular sauna use can significantly reduce the risk of the common cold.
- Heat stimulates the production of ‘heat shock proteins’, which protect cells and strengthen the immune response.
- The effect is amplified when sauna is combined with the cold shock (cold therapy).
How heat activates your inner defence
When you step into a sauna, your body responds to the heat by mimicking a mild fever. Fever is the body’s natural defence against infections, and the artificial fever created by the sauna puts the immune system on higher alert.
A Finnish study from 2026, published in the journal Temperature, examined the effect of a single 30 minute sauna visit with a brief cold shower halfway. The researchers found a marked rise in all types of circulating white blood cells, including neutrophils and lymphocytes, which are essential for fighting pathogens.
“This may indicate that sauna bathing mobilises extra white blood cells into the bloodstream from the tissues... This kind of periodic release is beneficial, since the cells can better patrol the body and respond to pathogens when they leave their storage sites,” said researcher Ilkka Heinonen from the University of Turku.
Heat shock proteins: the cell’s protective kit
Another central mechanism is the production of so-called heat shock proteins (HSPs). Cells produce these proteins in response to stressful conditions, including intense heat. HSPs play a key role in repairing damaged proteins and protecting cells from further harm.
Research shows that heat stress from sauna use increases the expression of HSPs, which not only protects cells, but also modulates the immune system by making immune cells more resilient and reducing pro-inflammatory cytokines. This contributes to an overall strengthening of the body’s defences.
Fewer sick days with regular sauna use
While a single sauna visit gives a temporary boost, it is the regular practice that brings the long term benefits. A classic study investigated the effect of regular sauna bathing on the incidence of the common cold. The results showed that the group using the sauna regularly, twice a week, experienced significantly fewer episodes of colds, especially in the last three months of the six month study period.
| Benefit of sauna use | Scientific explanation |
|---|---|
| Increased white blood cell count | Heat mobilises immune cells from tissues into the bloodstream, where they can fight infections. |
| Increased production of HSPs | Protects cells from stress and damage, and improves immune cell function. |
| Improved circulation | Helps transport immune cells more quickly around the body. |
| Reduced inflammation | May dampen chronic inflammation and promote healing. |
Combining heat and cold
In Nordic bathing culture, and especially at Heat Studio, saunagus, a guided sauna ritual, is often accompanied by cold therapy, such as a cold dip or ice bath. This contrast practice, alternating between extreme heat and intense cold, is thought to train the cardiovascular system and further stimulate the immune response.
The cold shock causes blood vessels to constrict rapidly, which pumps blood back towards the vital organs, while heat makes them dilate again. This “vascular gymnastics” promotes the clearance of waste products and optimises blood flow. Together, heat and cold create a strong approach that not only strengthens the immune system, but also improves recovery and wellbeing.
When should you avoid the sauna?
Although the sauna is beneficial for most people, there are times when you should stay away. If you have a fever, an active infection or you feel distinctly unwell, wait to visit the sauna until you are healthy again. The heat can put unnecessary strain on the body in these cases. Always speak to your doctor if you are in doubt, especially if you have cardiovascular disease or other chronic conditions.
Conclusion: Make sauna part of your routine
The science clearly suggests that regular exposure to heat stress can be a powerful tool for strengthening the immune system. By incorporating saunagus into your weekly routine, you can potentially reduce sick days and give your body the best conditions to stay healthy and strong all year round. At Heat Studio in Kokkedal you can experience Nordic bathing culture in its most authentic form, and give your immune system the boost it deserves.
Sources
- Ernst, E., Pecho, E., Wirz, P., & Saradeth, T. (1990). Regular sauna bathing and the incidence of common colds. Annals of Medicine, 22(4), 225-227. https://pubmed.ncbi.nlm.nih.gov/2248758/
- Heinonen, I. H. A., et al. (2026). Acute Finnish sauna heat exposure induces stronger immune cell than cytokine responses. Temperature. https://www.tandfonline.com/doi/abs/10.1080/23328940.2026.2645467
- Patrick, R. P., & Johnson, T. L. (2021). Sauna use as a lifestyle practice to extend healthspan. Experimental Gerontology, 154, 111509. https://www.sciencedirect.com/science/article/pii/S0531556521002916
- Pilch, W., et al. (2013). Effect of a single Finnish sauna session on white blood cell profile and cortisol levels in athletes and non-athletes. Journal of Human Kinetics, 39, 127-135. https://pmc.ncbi.nlm.nih.gov/articles/PMC3916915/
