Most writing about saunas is written by people selling them. So it is fair to ask the opposite question.
This article collects the documented risks and the people for whom a sauna is a bad idea. It sits under our overview of sauna health benefits. This is general information, not medical advice.
Short answer: for healthy people who keep sessions short and stay sober, medical reviews find saunas well tolerated. The main dangers are alcohol, dehydration, staying in too long, and using one with an unstable heart condition. Some people should stay out, and others should ask a doctor first.
What the reviews conclude
Two medical reviews looked at the risks directly.
A 2006 review in the International Journal of Circumpolar Health concluded: “Sauna was well tolerated and posed no health risks to healthy people from childhood to old age.” It added that baths “did not appear to be particularly risky to patients with hypertension” when they were medicated and stable, and it called for better-designed research.
A 2001 review in The American Journal of Medicine lists the exceptions: “Contraindications to sauna bathing include unstable angina pectoris, recent myocardial infarction,” along with other conditions.
The risks, ranked by how avoidable they are
| Risk | What the sources say | How to avoid it |
|---|---|---|
| Alcohol | Increases “the risk of hypotension, arrhythmia, and sudden death” (2001 review) | Don’t drink before or in the sauna |
| Dehydration | About a pint of sweat in a short session (Harvard Health) | Water before and after |
| Low blood pressure | A sauna “may cause blood pressure to fall” (Medical News Today) | Stand up slowly; ask a doctor if yours runs low |
| Staying too long | No more than 20 minutes at a time (Medical News Today) | Use a timer |
| Hot-to-cold shock | People with heart complaints or high blood pressure should avoid cold water after the hot room (thisisFINLAND) | Cool down gradually |
| Burns | The stove and stones are the hottest surfaces in the room | Keep clear; supervise children |
The burns row is my own addition, not from a cited source.
Alcohol is the big one
Every source that mentions alcohol says the same thing. Cleveland Clinic tells people who have been drinking to avoid the sauna.
A 1992 study shows the mechanism. In 10 healthy men, sauna alone left systolic blood pressure at baseline. Sauna with alcohol dropped it from 136 to 113 mmHg. The authors concluded “the risk of hypotension is increased when sauna bathing is combined with alcohol consumption.”
Low blood pressure in a hot room is how people faint, and fainting next to a stove is how they get hurt.
Who should stay out
Based on the sources above:
- Anyone with unstable angina or a recent heart attack (2001 review)
- Anyone with a recent stroke (Cleveland Clinic)
- Anyone who has been drinking (all sources)
- Anyone who is ill with a fever or infection (Cleveland Clinic)
Who should ask a doctor first
- Pregnant people, and people trying to get pregnant (Cleveland Clinic)
- People with heart conditions, including heart failure and high or low blood pressure (Cleveland Clinic)
- People with kidney disease, who “may be at a higher risk of dehydration” (Medical News Today)
- People with multiple sclerosis. Cleveland Clinic says saunas “should be used cautiously if you have MS and avoided if they trigger problems.”
Children
Medical News Today says children aged 6 and above can use a sauna with supervision, for no longer than 15 minutes at a time. It cites no study for that, so treat it as a conservative rule and ask your pediatrician.
Warning signs
Leave immediately if you feel dizzy, nauseated, weak, or short of breath. Cool down, sit, and drink water. If symptoms don’t pass quickly, get medical help.
Buying with safety in mind
A timer and a thermometer are cheap. The Harvia Thermo-Hygrometer costs $38.88. Infrared cabins run cooler, which some people tolerate better. The Dynamic Andora lists a 140°F maximum. Cooler is not the same as risk-free, and the cautions above still apply.
The home sauna buying guide covers heater guards and placement.
Bottom line: saunas aren’t bad for most healthy people. They are risky with alcohol, long sessions, or an unstable heart. If you are on either list above, the decision belongs to your doctor.
Sources
- Kukkonen-Harjula K, Kauppinen K, “Health effects and risks of sauna bathing,” International Journal of Circumpolar Health, 2006 (abstract): pubmed.ncbi.nlm.nih.gov
- Hannuksela ML, Ellahham S, “Benefits and risks of sauna bathing,” The American Journal of Medicine, 2001 (abstract): pubmed.ncbi.nlm.nih.gov
- Roine R, et al., “Alcohol and sauna bathing: effects on cardiac rhythm, blood pressure, and serum electrolyte and cortisol concentrations,” Journal of Internal Medicine, 1992 (abstract): pubmed.ncbi.nlm.nih.gov
- Medical News Today, “Sauna: Health benefits, risks, and precautions,” medically reviewed, last updated June 27, 2023: medicalnewstoday.com
- Cleveland Clinic, “Get Your Sweat On: The Benefits of a Sauna,” August 12, 2024, and “6 Possible Benefits of Infrared Saunas,” October 9, 2026: health.clevelandclinic.org
- Harvard Health Publishing, “Sauna Health Benefits: Are saunas healthy or harmful?” May 14, 2020 (opening section): health.harvard.edu
- thisisFINLAND, “Bare facts of the sauna in Finland,” accessed October 12, 2026: finland.fi
- Harvia and Dynamic Saunas listings (price, maximum temperature), checked October 2026