A reader sent us this question:
In a dry sauna, does the 175°F (79°C) or higher temperature kill bacteria and viruses that some one else has brought into the public sauna? Are there other cautions that you would have for the public sauna?
The short answer is no.
The most common disease that can be transmitted by contact with an surface that has been contaminated by someone is the Hepatitis virus. Research shows that Hepatitis can survive for more than 10 hours at temperatures as high as 140°F (60°C), and as long as six months at lower temperatures. To kill hepatitis, you need to bathe it in steam for two minutes at 250°F (121°C) or for four minutes in dry heat at 320°F (160°C). Complete sterilization to kill all pathogens requires 15 minutes in steam or two hours in dry heat.
Inside that sauna, the thermometer may read a high temperature, but that thermometer is usually placed near the ceiling. As you know, heat rises, so the temperature near the ceiling can be much hotter than the temperature at the benches or floor. Human skin will burn after contact with a surface at 130°F (54°C) for 30 seconds, and in less time at higher temperatures. So if you can walk unprotected on the sauna floor or sit on that sauna bench, you know that the temperature can not be hot enough to kill germs.
Steam rooms and hot tubs can be more dangerous, since these operate at lower temperatures. Hot tubs especially, which operate at close to body temperature, can become breeding grounds for dangerous bacteria if not properly maintained. For instance, the ideal conditions for bacteria like the ones that can cause Legionnaires Disease are temperatures from 95-115°F (35-46°C), which is the usual temperature range for most hot tubs and steam rooms.
So how can you protect yourself from germs in a sauna?
The easiest way is to put a barrier between yourself and others by always sitting on a towel. In Germany, proper sauna etiquette says that you should drape a large enough towel to prevent any part of your body from touching the wood of the sauna benches or walls. However, even sitting on a small gym towel will protect the most sensitive areas of your body from what has been left behind by others.
The sauna should be kept clean. Regularly washing the inside of the sauna with water and a disinfecting detergent is essential to keep it safe. The wood must be scrubbed to get any build up out of the cracks and crevices of the wood.
Steam rooms must be cleaned more regularly and vigorously with disinfectants, since there is more danger. Hot tubs need to have their chemistry checked regularly and daily water changes to keep them safe.
The smoke sauna or black banya is the cleanest of the saunas. This hard to find sauna bath that had an open stove had a natural disinfectant in the wood smoke and ash that covered all the surfaces inside of the sauna. Every time the sauna was heated, it got a full cleaning and disinfecting. Modern sealed or electric stoves do not have this same advantage.
Of course, as we have reported if you are sick, you should stay out of the sauna. If you get into the sauna and see someone hacking up a lung, it might be better to give them a few minutes by themselves.
Will I get sick in the sauna?
Even though the sauna does not kill germs, it is not a place that is known for causing illnesses. As we have reported before, people who use the sauna regularly are less likely to catch a cold. Millions of people use saunas every day, and it is very rare to find someone who was infected with a disease from using a sauna.
To be sure, rely on your senses. If the facility does not look clean or well maintained, it probably isn’t. If there are signs of mold or mildew, that should be a warning sign to find a different place. If they aren’t taking the time to clean the place, are they also taking shortcuts on other safety precautions like temperature controls or electrical connections? Those types of problems are more likely to hurt you than a disease.
Of course, if your immune system is compromised for any reason, you should discuss whether using a public sauna is right for you with a doctor.