The medical term for overheating when using a sauna is “hyperthermia”. It’s one of the positive effects you’re actively looking to achieve by using the sauna. In effect, you’re voluntarily subjecting your body to extreme conditions – with the standard sauna temperature between 90°C and 100°C followed by cooling down, sometimes at below 0°C. Whilst in the sauna, the temperature of your skin rises faster and differently to the temperature inside your body, which never actually increases by more than 1-2°C. After around 10 minutes in the sauna, however, the temperature of your skin increases to 40-42°C. It significantly stimulates and increases the turnover of various substances – your metabolic rate, in other words. Raising your body temperature from 37°C to 38°C or 39°C is like having an artificial fever. Unlike your body itself, numerous bacteria and viruses which can make us ill are unable to cope with such high temperatures, which means that using a sauna is an effective way of combating infections before they attack.