Does sauna bathing help against infections?

The hope that sauna bathing strengthens your immune defences is understandable, but the evidence for it is lacking. There is only one theoretical article suggesting that mild heat stress might improve resistance to infections. No concrete study results are presented in it. It remains speculation, not an established benefit.

More concrete is the evidence on the other side of the scale: the sauna as a potential source of infection. During an outbreak of a serious skin bacterium (MRSA) in a religious community, sauna use turned out to be a strikingly strong risk factor. People who had used the sauna had nearly nineteen times the chance of infection compared with people who had not. The sauna presumably served as a transmission site for the bacterium.

In addition, a biofilm of Mycobacterium avium has been found on sauna walls. This is a bacterium that can cause serious infections, particularly in people with a weakened immune system. This type of research does not prove direct disease, but it does show that the sauna environment can harbour infectious agents.

For people undergoing peritoneal dialysis (kidney dialysis via an abdominal catheter), international guidelines explicitly state that no studies exist that declare sauna use to be safe. For this group, it is advised against.

In short: there is no reliable evidence that sauna bathing helps prevent infections, but there are concrete indications that poorly maintained or heavily frequented saunas pose an infection risk, especially if your immune system is vulnerable.