What does a sauna do to your body?
In a sauna, skin temperature rises toward 104 °F (40 °C), the heart speeds up to about 140 beats a minute and you sweat nearly half a liter (about 1 lb) in 20 minutes (Sohar, 1976). On leaving, blood pressure drops a little: from 137/82 to 130/75 on average after a 30-minute session (Laukkanen, 2018).
Simplified diagram, not to scale. Dotted curves are estimates based on published measurements; the figures in the notes are measured.
What does a sauna do to your body?
A person sitting in a sauna, with a patch of their skin greatly magnified. Choose a situation, then tap a label on the drawing to learn what it is.
Sources: dry sauna at 176 to 194 °F, 80 to 90 °C (Sohar et al., Isr J Med Sci, 1976); steam bath at 113 to 122 °F, 45 to 50 °C (Shoenfeld et al., Arch Phys Med Rehabil, 1976); blood pressure after the session (Laukkanen et al., J Hum Hypertens, 2018); review (Laukkanen et al., Mayo Clin Proc, 2018); risks and alcohol (Hannuksela and Ellahham, Am J Med, 2001; Kukkonen-Harjula and Kauppinen, 2006). Drawing not to scale; scene timings and live heart: estimates. Pulse next to the heart: 143 bpm in the dry sauna after 20 minutes (Sohar, 1976), 113 and 135 bpm in the steam bath after 10 and 20 minutes (Shoenfeld, 1976); 70 bpm at the start and the values in between are our own rough estimate, to be checked.
Keyboard: 1 to 3 situations, Space pause, L slow motion, R restart, ← → previous or next step.
Frequently asked questions about saunas
How long should you stay in a sauna?
A sauna session usually lasts 5 to 20 minutes, in air at 176 to 212 °F (80 to 100 °C), and can be repeated one to three times with a cool break in between (Kukkonen-Harjula, 2006; Laukkanen, 2018). After 20 minutes of dry sauna, core temperature reached 101.5 °F (38.6 °C) and pulse 143 a minute (Sohar, 1976). In a more humid steam bath, the authors of one study felt it was risky to stay more than 10 minutes (Shoenfeld, 1976). Get out sooner if you feel unwell.
Does a sauna help you lose weight?
No, a sauna does not make you lose weight: the weight lost is mostly water, which comes back as soon as you drink. In 20 minutes of dry sauna, you lose about 457 grams (about 1 pound) of sweat (Sohar, 1976). The heart works harder, but a session does not replace real physical activity for burning fat. Drink water after the session to replace what was lost.
Is a sauna good for your heart?
Frequent sauna use goes with fewer heart deaths, but this is an observed link, not proof. In 2,315 Finnish men followed for about 20 years, those who used the sauna 4 to 7 times a week had a 63% lower risk of sudden cardiac death than those who went once a week (Laukkanen, 2015). Right after a 30-minute session, blood pressure drops a little and arteries are more flexible (Laukkanen, 2018). Saunas are not advised with unstable angina, a recent heart attack or severe narrowing of the aortic valve (Hannuksela, 2001).
Can you use a sauna while pregnant?
In a healthy woman whose pregnancy is going well, saunas showed no harmful effect in Finnish studies (Hannuksela, 2001; Kukkonen-Harjula, 2006). These studies mostly involve women used to saunas since childhood. With a complicated pregnancy, such as preeclampsia, saunas are not advised. Before going, it is best to talk with the midwife or doctor following the pregnancy, and to keep sessions short.
Why do you feel dizzy when you get out of a sauna?
You feel dizzy getting out of a sauna because blood pressure drops when you stand up: blood is still in the skin and legs. Skin vessels have opened to release heat, and the brain gets a little less blood for a few seconds. The risk is higher with blood pressure medication (Kukkonen-Harjula, 2006) or after drinking alcohol (Hannuksela, 2001). Stand up slowly, sit down if you feel dizzy, and drink some water.
True or false?
Sweating in a sauna melts fat.
False. Sweat is water and salt, not fat. The 457 grams (about 1 pound) of sweat lost in 20 minutes of dry sauna (Sohar, 1976) come back as soon as you drink.
Blood pressure drops a little after a sauna session.
True. In 102 people, right after 30 minutes in a sauna at 163 °F (73 °C), blood pressure went from 137/82 to 130/75 mm Hg on average (Laukkanen, 2018). That is also why you can feel dizzy when standing up.
It is proven that saunas help you live longer.
False. Finnish men who used the sauna often died less often over 20 years of follow-up (Laukkanen, 2015), but this is an observed link: they may also have been healthier to begin with. Randomized trials are still needed to prove it (Laukkanen, 2018).
This page as text
The same information as the charts, to read without animation: for each chart, the values at the main moments, then the notes with their level of evidence.
What happens during 20 minutes in a sauna?
In the sauna, the skin heats up first, then the heart speeds up and the core of the body rises by more than one degree. On stepping out, blood pressure drops: that is when dizziness comes. Estimated curves, as relative levels.
| Minutes in the sauna or sessions per week | Skin heat (dotted) | Heart rate (dotted) | Temperature inside the body (dotted) | Blood pressure (dotted) | What happens |
|---|---|---|---|---|---|
| In | 15 | 10 | 5 | 60 | Stepping into the sauna |
| 5 min | 70 | 35 | 18 | 59 | in the sauna |
| 10 min | 88 | 62 | 42 | 56 | in the sauna |
| 15 min | 94 | 80 | 64 | 55 | in the sauna |
| Out | 96 | 90 | 80 | 52 | Stepping out of the sauna |
| +10 min | 40 | 26 | 55 | 47 | 10 min after stepping out |
| +20 min | 25 | 15 | 30 | 49 | 20 min after stepping out |
Key points
- Skin at 104 °F, heart at 143 (During the session, Shown in humans)
In a sauna at 176 to 194 °F (80 to 90 °C), with 30 to 40% humidity, 60 people were followed: after 20 minutes, skin was at 104.7 °F (40.4 °C), the body core (rectal measurement) at 101.5 °F (38.6 °C), pulse at 143 beats a minute, and each had lost 457 grams (1 lb) of sweat. Source: Sohar, Shoenfeld and Shapiro, « Effects of exposure to Finnish sauna », Isr J Med Sci, 1976 - Like moderate exercise (During the session, Shown in humans)
The vessels of the skin open to get rid of heat and the heart pumps more blood: pulse can rise to 120 to 150 beats a minute, as during moderate exercise. Usual sessions last 5 to 20 minutes, at 176 to 212 °F (80 to 100 °C). Source: Laukkanen, Laukkanen and Kunutsor, « Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence », Mayo Clin Proc, 2018 - Careful when standing up (From stepping out to 3 min after stepping out, Shown in humans)
On standing up, a lot of blood is still in the skin and legs: blood pressure can drop suddenly, with dizziness. This risk is greater with blood pressure medication. Source: Kukkonen-Harjula and Kauppinen, « Health effects and risks of sauna bathing », Int J Circumpolar Health, 2006 - Blood pressure drops afterward (After stepping out, Shown in humans)
In 102 people, right after 30 minutes in a sauna at 163 °F (73 °C), blood pressure went on average from 137/82 to 130/75 mm Hg, and arteries were more flexible: pulse wave velocity went from 9.8 to 8.6 meters per second. Source: Laukkanen et al., « Acute effects of sauna bathing on cardiovascular function », J Hum Hypertens, 2018 - No alcohol (Throughout, Shown in humans)
Drinking alcohol in the sauna raises the risk of a drop in blood pressure, heart rhythm problems and sudden death: better to avoid it. Source: Hannuksela and Ellahham, « Benefits and risks of sauna bathing », Am J Med, 2001 - Estimated curves (Throughout, Hypothesis)
The shape of the curves follows published measurements; the heights are relative levels, not measurements. The drop in blood pressure on standing up and the return to rest after stepping out are estimated.
Does going to the sauna often help you live longer?
In Finnish men followed for 20 years, those who went to the sauna 4 to 7 times a week died less often of heart disease. This is an observed link, not proof that the sauna is the cause. Measured risks, 100 = 1 session a week.
| Minutes in the sauna or sessions per week | Risk of sudden cardiac death | Risk of dementia | Deaths during follow-up, in % | What happens |
|---|---|---|---|---|
| 1 | 100 | 100 | 49 | session of sauna a week |
| 2 | 78 | 78 | 38 | sessions of sauna a week |
| 3 | 78 | 78 | 38 | sessions of sauna a week |
| 4 | 37 | 34 | 31 | sessions of sauna a week |
| 5 | 37 | 34 | 31 | sessions of sauna a week |
| 6 | 37 | 34 | 31 | sessions of sauna a week |
| 7 | 37 | 34 | 31 | sessions of sauna a week |
Key points
- 1 session a week: the reference (1 session a week, Shown in humans)
The study followed 2,315 men aged 42 to 60 in eastern Finland, for about 20.7 years. In the 1 session a week group, 49.1% had died by the end of follow-up. Source: Laukkanen et al., « Association between sauna bathing and fatal cardiovascular and all-cause mortality events », JAMA Intern Med, 2015 - 2 to 3 sessions (From 2 to 3 sessions a week, Shown in humans)
The risk of sudden cardiac death was 22% lower (hazard ratio 0.78), but this result could have been due to chance. Deaths from all causes: 37.8%. Source: Laukkanen et al., « Association between sauna bathing and fatal cardiovascular and all-cause mortality events », JAMA Intern Med, 2015 - 4 to 7 sessions (From 4 to 7 sessions a week, Shown in humans)
The risk of sudden cardiac death was 63% lower (hazard ratio 0.37). Deaths from all causes: 30.8%. Source: Laukkanen et al., « Association between sauna bathing and fatal cardiovascular and all-cause mortality events », JAMA Intern Med, 2015 - What about dementia? (From 2 to 7 sessions a week, Shown in humans)
In the same group of men, the risk of dementia was 22% lower with 2 to 3 sessions (0.78, not certain) and 66% lower with 4 to 7 sessions (0.34); that of Alzheimer's disease, 65% lower (0.35). Source: Laukkanen et al., « Sauna bathing is inversely associated with dementia and Alzheimer’s disease in middle-aged Finnish men », Age Ageing, 2017 - Duration matters too (Whatever the number of sessions, Shown in humans)
Compared with sessions of less than 11 minutes, sessions of more than 19 minutes went with a 52% lower risk of sudden cardiac death (hazard ratio 0.48). Source: Laukkanen et al., « Association between sauna bathing and fatal cardiovascular and all-cause mortality events », JAMA Intern Med, 2015 - A link, not proof (Whatever the number of sessions, Hypothesis)
These are observations: men who go to the sauna often may also be healthier or more active. Only trials in which people are randomly assigned to the sauna could prove an effect, and they are still lacking. Source: Laukkanen, Laukkanen and Kunutsor, « Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence », Mayo Clin Proc, 2018
Dry sauna, steam room or hot bath: which heats the body most?
The dry sauna and the steam bath (hammam) raise the body core by about 2.7 °F (1.5 °C) in 20 minutes; a hot bath at 99.5 °F (37.5 °C) does so much more slowly. Curves estimated between measurements, scale from 98.6 to 102.2 °F (37 to 39 °C).
| Minutes in the sauna or sessions per week | Dry sauna, 176 to 194 °F (dotted) | Steam bath, 113 to 122 °F (dotted) | Hot bath, 99.5 °F (dotted) | What happens |
|---|---|---|---|---|
| In | 0 | 0 | 0 | Stepping into the heat |
| 5 min | 12 | 20 | 3 | in the heat |
| 10 min | 40 | 55 | 7 | in the heat |
| 15 min | 62 | 66 | 11 | in the heat |
| 20 min | 80 | 75 | 15 | in the heat |
Key points
- Dry sauna: 101.5 °F (38.6 °C) in 20 minutes (Throughout, Shown in humans)
In the hot, dry air of a sauna at 176 to 194 °F (80 to 90 °C), rectal temperature reached 101.5 °F (38.6 °C) after 20 minutes, skin 104.7 °F (40.4 °C), with 457 grams (1 lb) of sweat. Source: Sohar, Shoenfeld and Shapiro, « Effects of exposure to Finnish sauna », Isr J Med Sci, 1976 - Steam room: sweat does not dry (Until 10 min, Shown in humans)
In a steam bath at 113 to 122 °F (45 to 50 °C) and 100% humidity, rectal temperature reached 100.6 °F (38.1 °C) at 10 minutes and 101.3 °F (38.5 °C) at 20 minutes, with a pulse of 113 then 135. Sweat cannot evaporate in saturated air: the authors considered it risky to stay more than 10 minutes. Source: Shoenfeld, Sohar and Ohry, « Heat stress: comparison of short exposure to severe dry and wet heat in saunas », Arch Phys Med Rehabil, 1976 - Hot bath: slower, less sweat (From 10 min, Shown in humans)
In a bath at 99.5 °F (37.5 °C) for 60 minutes, rectal temperature rose to 100.2 °F (37.9 °C) at most, and pulse went from 64 to 90. For the same rise, people sweated less than in a hot, dry room at 156 °F (69 °C): 566 versus 815 milliliters. Source: Su, Hoekstra and Leicht, « Hot water immersion is associated with higher thermal comfort than dry passive heating for a similar rise in rectal temperature and plasma interleukin-6 concentration », Eur J Appl Physiol, 2024 - Estimated curves (Throughout, Hypothesis)
The measured points are in the notes; the starting temperature (98.6 °F, 37 °C) and the shape between measurements are estimated. The three studies were not done on the same people.
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