New research reveals what a sauna can do for your immune system

Author: Newstalk ZB,
Publish Date: Sun, 2 Aug 2026, 11:45am

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You probably think of a sauna as somewhere to relax, recover after exercise, or simply warm up on a cold day.

However, scientists have discovered that just 30 minutes in a sauna may temporarily change the way your immune system behaves.

New research published in the journal Temperature found that just one single sauna session caused every major type of white blood cell to increase in the bloodstream. These are the cells that help defend you against infections, clear away damaged cells and coordinate your body's immune response.

Most of the time, many of these cells aren't constantly travelling around your body. Instead, they wait in places like your bone marrow, spleen and lymph nodes until they're needed.

You can think of them like emergency services. You don't keep every police officer, firefighter and ambulance driving around every street all day. Most are stationed at their bases, ready to respond when something happens.

But every now and then, it can be useful to have more of them out on patrol.

That's essentially what the researchers think happened during the sauna. The heat appeared to temporarily send more immune cells into circulation, giving them the opportunity to move through the body looking for signs of infection, damaged tissue or anything else that doesn't belong.

Scientists call this immune surveillance.

In the experiments the researchers recruited 51 adults with an average age of 50. Each volunteer spent 15 minutes in a traditional Finnish sauna heated to around 73°C, cooled off with a two-minute shower, then returned to the sauna for another 15 minutes. Blood samples were taken before the sauna, immediately afterwards and again 30 minutes later, allowing the researchers to watch how the immune system responded in real time.

Blood tests revealed that every major type of white blood cell increased immediately after the sauna. Neutrophils, the body's first responders to infection, and lymphocytes, which help recognise and destroy infected cells, both surged into the bloodstream before returning to their usual levels about 30 minutes later.

That suggests these cells weren't being created from scratch. Instead, they were temporarily moving out of their storage sites and into circulation before returning home again.

The scientists also measured 37 different cytokines, the chemical messenger molecules that immune cells use to communicate with one another. Surprisingly, despite the dramatic movement of white blood cells, very few of these signalling molecules changed. The researchers think this means the immediate response to a sauna is driven more by moving immune cells around the body than by switching the immune system into a highly inflammatory state.

While the study didn't go on to look at whether people who regularly took saunas had a stronger immune system, it does show that your immune system isn't sitting still while you're relaxing, but instead is working harder than ever.

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