Independent guide for the UK
Is a sauna good for your heart? How long should you stay in, and is infrared as good as the real thing? We read the studies, grade the evidence behind each claim and explain how to use heat and cold water safely, so you know what a session can and can't do.
Each common claim, graded by the quality of the studies behind it. Regular saunas have some of the best long-term data of any wellness habit, but most of it comes from one region of Finland, and many popular claims have none at all.
Decades-long Finnish studies link frequent saunas with far fewer heart deaths and strokes, and short trials show helpful changes in blood vessels. Not yet tested in long randomised trials.
A session lowers blood pressure for a while, an 8-week trial found a lasting fall when saunas followed exercise, and a cohort study linked frequent use with less hypertension.
One cohort of Finnish men found much less dementia among frequent users. It has not been repeated elsewhere.
One small randomised trial of medical whole-body heating eased depression for six weeks. That was not a sauna, and no sauna trial has tested it.
Most regular users say they sleep better, but that comes from surveys, not trials.
Small trials of 6 to 10 people hint at better endurance and recovery.
One Finnish cohort linked frequent saunas with less pneumonia and lung disease.
One small study found regular users had a more stable skin barrier.
Sweat carries tiny amounts of toxins compared with your kidneys, and the weight you lose is water that comes back when you drink.
Since 1984, researchers in Kuopio have followed thousands of people and asked how often they use a sauna. The more often, the lower the risk of several major diseases. What these results do and don’t prove.
Many UK sauna clubs pair the heat with a cold plunge or a dip in the sea. The cold has real effects on muscle soreness and mood, a smaller evidence base than the heat, and one serious risk: the gasp reflex that comes with sudden immersion. Here is what the trials show and how to do it safely.
Cold water and contrastA Finnish sauna, an infrared cabin and a steam room work at very different temperatures and humidity, and most of the research used the first. Every type compared.
Six guides, in the order most people need them: what a sauna is, what it does, how to use one, cold water, safety and buying your own.
Short answers, each linked to the guide that explains it in full.
A traditional sauna is hot and fairly dry, typically 70°C to 100°C with 10% to 20% humidity, rising briefly when water is thrown on the stones. A steam room is much cooler, about 40°C to 50°C, but close to 100% humidity, so sweat can't evaporate.
Nothing is proven in the strict sense, because there are no long randomised trials. The best evidence is for the heart and circulation: long Finnish studies link frequent sauna use with fewer heart deaths, strokes and cases of high blood pressure, and short trials show a session lowers blood pressure and makes arteries more flexible for a while.
Start with 5 to 10 minutes on a lower bench and see how you feel. You can add time and rounds over a few weeks. Leave whenever you feel dizzy, sick or uncomfortable.
No. A cool shower or fresh air works fine. The long-term Finnish sauna studies didn't depend on cold plunges, and cold water carries risks of its own.
The most common are feeling light-headed or faint on standing, headache, and dehydration. Overheating, heat exhaustion and, rarely, heatstroke can happen if you stay in too long, especially after drinking. Men who use saunas often may have a temporary drop in sperm count.
Often not. Garden buildings usually fall under permitted development if they meet the size, height and position limits on the Planning Portal, such as staying under 2.5 metres high within 2 metres of a boundary. Rules differ for listed buildings, flats and designated land, so check with your council.