Sauna and Alcohol: Why It's a Dangerous Mix

A sauna already puts the body under real strain: heat raises your heart rate, opens up (dilates) your blood vessels, and makes you lose fluid and salts through heavy sweating. Alcohol pushes every one of those effects further in the wrong direction.

• Dehydration stacks up. Alcohol is a diuretic, so it makes you pass more fluid at the same time as the sauna is sweating it out - a double hit that can leave you badly dehydrated.
• Blood pressure drops. Both heat and alcohol dilate blood vessels and lower blood pressure. Together they can drop it far enough to cause dizziness, fainting and collapse - especially in the standing rush as you leave the sauna.
• The heart is strained. A racing heart from the heat, combined with dehydration and alcohol, raises the risk of an irregular heartbeat (arrhythmia).
• Thermoregulation fails. Alcohol interferes with the body's ability to sense and control its own temperature, so you may not notice you are dangerously overheating until it is too late.
• Judgment goes. Alcohol makes people stay in longer, ignore warning signs and take risks they would not sober - including falling asleep in the heat.

Sauna bathing is very safe for healthy people, and deaths are rare - Finnish forensic work puts sauna-related deaths at well under two per 100,000 people a year. But when deaths do happen, alcohol is a recurring theme. A Finnish study of sauna deaths (Kenttamies and Karkola, Journal of Forensic Sciences) found that around half of all cases involved alcohol, and other analyses put the figure higher still. Most victims were middle-aged men, and heat exposure was the direct cause in a significant share of cases.

Researchers concluded that as well as alcohol's immediate effect on the body's temperature control, heavy drinking over time may make fatal overheating more likely. The pattern is consistent: the danger is not the sauna on its own, but the sauna combined with alcohol.

The safest approach is to keep alcohol and the sauna completely separate. Do not drink beforehand, and do not take alcohol in with you. If you have been drinking, skip the sauna until the alcohol has fully cleared your system and you are properly rehydrated - that means waiting several hours, not minutes, and longer after a heavy session.

The classic sauna-and-a-few-beers social occasion is exactly the scenario the forensic data warns about. If a sauna is part of a night out, treat it as an either/or: enjoy the sauna first while sober and well hydrated, or leave it for another day.

Hydration is the whole point, so make it work for you rather than against you:

• Water before, between rounds and after - the simplest and best option.
• An electrolyte drink for longer or more frequent sessions, to replace the salts lost in sweat.
• Herbal or fruit teas, or plain sparkling water, if you want something with more flavour.

Save any alcoholic drink for well after you have finished, cooled down and rehydrated. For general guidance on sensible drinking, see the NHS alcohol advice.

Alcohol aside, the sauna is not right for everyone. Give it a miss, or check with a GP first, if you have been drinking, feel unwell or dehydrated, have a fever, or have a heart condition, uncontrolled blood pressure, or are pregnant. Our guide to who should not use a sauna covers this in full, and sauna and cardiovascular health explains how heat affects the heart.