Finnish Sauna

In a 2019 randomized trial of 21 people, systolic blood pressure fell from 123 ± 15 to 105 ± 11 mmHg (P < 0.01) during the 1 × 10 condition. A 2017 cohort study associated more frequent sauna sessions with lower incident hypertension, but a 2023 randomized trial of 41 people found no difference between interventions in cf-PWV or systolic or diastolic blood pressure.

In a 2021 quasi-experimental study of 26 healthy people, peak core temperature fell by − 0.3 °C [− 0.2, − 0.4]. A separate randomized trial of 10 people found higher chest skin temperature after mist sauna than after showering at 9:00.

In a 2023 randomized trial of 41 people, resting core temperature after the sauna intervention was lower by -0.27°C [-0.54, -0.01] (P = 0.046). A 2021 study of 26 people also found lower peak T_rec in both females and males (− 0.3 °C [− 0.2, − 0.4], time: p < 0.001).

A 2021 randomized trial of 54 people found increases in maximal strength values in both hands, with higher values than controls in the trained and untrained hands after the intervention. In contrast, a 2025 systematic review of randomized trials found that IRS and HWI did not improve recovery of isometric strength production compared with the control condition in the remaining four studies.

A 2008 quasi-experimental study of 45 people found improvements in both measured anxiety measures after sauna bathing. A cross-sectional study also reported decreased anxiety or mild depression among sauna users, but this does not show that sauna use caused the change.

In a quasi-experimental study of 20 healthy people, the P300 area decreased in the sauna group but not the control group. This change in a measured response does not by itself show improved everyday cognitive function.

A quasi-experimental study of 20 healthy people found that reaction time decreased in the sauna group but not the control group. The study measured reaction time; it does not establish an improvement in concentration in daily life.

Two quasi-experimental studies reported increases in HDL cholesterol after repeated sauna baths, including a 23.6% increase in a study of 12 people. Findings differ: a 2014 study of 16 people found that HDL remained only slightly increased after the 10th session, without statistical significance.

A 2019 quasi-experimental study of 93 people found changes in time and frequency-domain HRV variables during the cooling down period after sauna bathing, which the study interpreted as indicating a dominant role for parasympathetic activity and decreased sympathetic activity.

A quasi-experimental study of 45 people found improvement on the depression-dejection mood scale after sauna bathing. Findings differ: a randomized trial of 37 people found no improvement in depression compared with control.

A 2025 cross-sectional study reported a higher rating for sleeping well after sauna use than before: 3.01 (.79) versus 3.29 (.83). Findings differ across studies: a randomized trial of 37 people found no improvement in sleep compared with control, while a review described increased deep sleep after sauna bathing.

Small quasi-experimental studies reported decreases in total cholesterol and LDL cholesterol during 3 weeks of sauna treatment and in the week afterwards, and after repeated sauna baths. Findings are not consistent: a 2025 study of 12 people reported LDL cholesterol after sauna as 87 ± 16 NS (Table 1).

A 2021 randomized trial of 36 people found that maximal breath frequency increased at the end of the intervention; the result does not establish whether this change is beneficial.

A 2019 quasi-experimental study of 37 people found lower VNRS and ODI scores after dry sauna therapy (P < 0.001 for both); median ODI scores were 12 (2–24) before and 8 (1–17) after. A 2025 narrative review also described improved perceived physical function in patients with PAD compared with a sham group.

A 2025 cross-sectional study reported decreased stress among sauna users. A separate quasi-experimental study of 8 people found cortisol decreased at 80 D and 100 D, so the studies measured different stress-related outcomes.

A quasi-experimental study of 20 healthy people found increased NO x concentrations in both groups after the first sauna bath.

A quasi-experimental study of 16 people found a decline in triacylglycerols after the first sauna session and 24 hours after the 10th session. A study of 12 athletes also reported a 12.7% decrease after sauna.

A 2014 randomized trial of 43 healthy men reported that a single Finnish sauna bath reduced oxidative stress induced by a 30-min aerobic exercise. A 2020 quasi-experimental study of 20 people found increased total antioxidative status after a series of sauna baths in the T group.

A 2019 quasi-experimental study of 37 people recorded a decrease in heart rate from 75.4 ± 10.4 before to 71.1 ± 10.3 after dry sauna therapy (P = 0.003). In a 2021 study of 26 people, resting heart rate also fell, but the reduction was not superior to that from normal training alone.

In a 2025 cross-sectional study, responses for “No bodily pain” rose from 2.68 (.89) to 3.10 (.93) on a 4-point Likert scale (n=383; p<.001). A 2025 narrative review described decreases in pain scores alongside increases in 6-minute walk distance, ankle-brachial index, and blood flow measured by laser doppler perfusion imaging.

A cross-sectional study of 41 healthy volunteers found increased stratum corneum hydration among people who used a sauna regularly.

In a 2008 quasi-experimental study of 45 people, the Profile of Mood States Fatigue subscale improved after sauna bathing; a decrease on this subscale is an improvement.

A quasi-experimental study of 45 people found improvement on the anger-hostility subscale of a mood questionnaire after sauna bathing; a decrease on this scale indicated improvement.

A 2026 pilot study of 18 people with HFpEF reported improved body composition, muscle function, exercise capacity, and QoL. Results differ from a 2020 quasi-experimental study of 38 people, which found no significant changes in body composition before and after the 8-session sauna therapy.

In a quasi-experimental study of 15 people with heart failure, peak respiratory oxygen uptake increased from 13.3 +/- 1.8 to 16.3 +/- 2.1 mL/kg/min.

A 2025 narrative review reports that frequent users (four to seven sessions per week) had lower levels of high-sensitivity C-reactive protein (hsCRP) and reduced leukocyte counts, both markers of systemic inflammation.

Expert knowledge proposes that sauna promotes excretion of heavy metals (e.g., lead, cadmium, mercury) and lipophilic toxins via sweat, supporting phase II detoxification pathways. Some community reports also describe this effect.

The proposed mechanism is that heat exposure followed by cooling activates the parasympathetic nervous system, which may enhance vagal tone and promote recovery.

An expert-knowledge claim describes acute sauna exposure as increasing growth hormone levels by up to 2–5 fold, especially with repeated sessions and proper hydration.

The proposed mechanism is that sauna heat stress induces heat shock proteins (HSP70), which support mitochondrial biogenesis and efficiency.

In a qualitative study of 11 people, participants described psychological effects extending into daily life, including reduced feelings of isolation, improved mood, pain relief and clearer thought.

Studies did not support heat methods for reducing muscle soreness: a review found that only one of three studies measuring soreness observed relief compared with passive recovery.

Studies did not support faster muscle recovery: in a 2019 quasi-experimental study of 16 people, sustained isometric submaximal contraction did not provoke greater neuromuscular fatigability.

Studies did not support faster wound healing: a 2003 randomized trial of 79 people found no differences in wound healing between the two groups.

The evidence summary does not support prolactin reduction as an established effect; a 2021 quasi-experimental study of 30 people recorded PRL decreasing from 14.50 to 13.71 ng/ml.

Studies did not support a testosterone increase: a 2021 quasi-experimental study of 30 people found no significant changes (p >.05) in the concentrations of the remaining hormones, with TES increasing from 4.04 to 4.24 ng/ml.

Studies did not support hydration improvement: a 2003 quasi-experimental study of 25 people found no significant differences in any body water compartments before and after the sauna bath or after the rest period.

Studies did not support blood glucose level support: a 2025 quasi-experimental study of 12 people found glucose levels significantly elevated after sauna (p < 0.001), with capillary glucose, mg/dL, rising from 84.7 to 99.2.

Studies did not support improved insulin sensitivity: in a 1985 randomized trial of 6 people, the insulin response to a glucose challenge was lower during heating (P less than 0.001) than under thermoneutral conditions (23 degrees C).

A trial involving 10 patients with untreated hypertension did not claim a therapeutic benefit. A separate study of 133 patients reported improved blood pressure regulation with sauna and kinesiotherapy.

In a trial of 41 adults with stable coronary artery disease, sauna use did not produce a vascular benefit. A separate study of 133 patients with coronary heart disease, including people after bypass surgery, reported only a hemodynamic benefit.

An observational cohort of 2,315 people found lower Alzheimer’s disease incidence among those attending sauna 4-7 sessions per week. A later review reported 65% lower Alzheimer’s risk and 66% lower dementia risk at 4–7 sessions/week, and 53% reduced dementia risk in another Finnish cohort.

A cohort study's authors said sauna bathing can be recommended for children with bronchial asthma. In cross-sectional reports from 384 people, sauna bathing was described as alleviating asthma symptoms.

A controlled trial involving 50 people associated sauna bathing with fewer colds, but a separate review found symptom reduction only on day 2, not through days 3, 5 or 7. These findings do not show a sustained reduction in cold symptoms.

A review of small studies reported improvements in mood, fatigue and somatic complaints among people with depression. Heat intolerance was common in the populations studied.

A single-arm pre/post study of 13 female patients meeting ACR criteria found reductions in pain VAS and FIQ scores after Waon therapy.

A pooled review reported improved peak nasal inspiratory flow and FEV1 in a trial involving people with allergic rhinitis.

A single-arm study of 37 patients with chronic low back pain found reductions in pain and ODI scores after dry sauna therapy.

A review of small studies reported improvements in mood, fatigue and somatic complaints among people with chronic fatigue syndrome. Heat intolerance was common in the populations studied.

An observational cohort of 2,315 people found lower dementia hazard among those having 4-7 sauna sessions per week.

A pilot study described decreases in pain and stiffness during sauna sessions in people with rheumatoid arthritis.

An observational cohort of 2,221 people associated frequent sauna bathing with lower incidence of psychotic disorder, but a causal role was not established.

An observational cohort of 2,242 middle-aged men linked 2-3 sauna sessions per week to lower incident venous thromboembolism risk; sauna was not tested as a treatment.

An observational cohort of 1,628 people associated frequent sauna bathing with reduced risk of incident stroke.

One small study found increased deep sleep and reduced wakefulness after a sauna session.

Sauna therapy is proposed to ease chronic pain through muscle relaxation, improved circulation and endorphin release, and is used in multimodal pain programs.

Sauna has not been shown to treat anxiety disorder. In cross-sectional reports from 384 people, some women said sauna reduced anxiety, while others with anxiety described panic-like symptoms triggered by rising heat and heart rate.

A cohort study of 2,071 people found no association between frequent sauna bathing and incident chronic kidney disease (HR 0.84, 95% CI 0.46-1.53) during a 25.7-year follow-up, so the studies did not support this indication.

A quasi-experimental study found that male students lost 0.65±0.24 kg of bodily fluids after a 60-minute experiment involving 4 sauna sessions of 10 minutes each, with four 5-minute breaks. A separate trial reported dehydration with decreased body weight and urine volume.

A 2018 review reported lowered sperm count (93 ± 27.0 ×10^6 vs 223 ± 52.8 ×10^6, p < 0.001), lowered sperm concentration (31 ± 13.1 ×10^6/ml vs 89 ± 29.3 ×10^6/ml, p < 0.001), and fewer motile sperm (36.1 ± 3.6% vs 58.0 ± 7.6%, p < 0.01). A 2022 quasi-experimental study involving 20 people found cortisol increased significantly after sauna bathing and described it as a greater stress on the endocrine system than exercise in a hot environment for both athletes and non-athletes.

A 2025 pooled analysis of randomized trials found that all-out swimming performance in young swimmers and triathletes deteriorated after post-exercise sauna bathing at 80–85 °C for 3 × 8 min; overall time and first split time were slower, with an effect of 1.69%. A 2021 trial also found a greater handgrip fatigue index in heated participants during sessions.

In a 2023 quasi-experimental study of 22 people, at 120°C, tension (13.05→20.50), depression (8.50→12.23), fatigue (7.86→13.27), and confusion (4.05→13.50) increased significantly (p < 0.001), while vigor decreased (15.41→2.36, p < 0.001); the anger change was non-significant.

A review of randomized and non-randomized human studies reported lower blood pressure alongside hypovolemia, increased urination, and decreased body weight. In one trial, 21 people developed hypotension (<90/60 mmHg) during the second 10-min sauna exposure.

A quasi-experimental study reported loss of consciousness during a 120°C session among 22 people; a separate cross-sectional study of 384 people also reported fainting.

A 2020 cohort study of 13,994 people found an elevated risk during the first 20 years among those exposed to sauna temperatures of 100 °C or more compared with those exposed to temperatures under 80 °C (HR = 2.04, 95% CI = 1.32–3.15).

In a quasi-experimental study of 45 people, heart rate reached up to 160 bpm, a difficult-to-maximal effort range. Another study found a greater heart-rate increase after sauna bathing in non-athletes than in athletes.

In a quasi-experimental study of 45 people, blood pressure reached the stage 1 hypertension range, with a mean of 140/94 mmHg during the fourth session. Another study found that systolic blood pressure increased after exercise in elevated temperatures and after the sauna.

A 2025 review of randomized trials noted that whole-body heat exposure can add stress to an athlete’s total load and recovery regime; it did not report that overtraining syndrome occurred.

A 2023 cohort involving 209 people recorded contusions/distorsions.

A 2023 quasi-experimental study involving 22 people recorded vomiting directly preceding fainting.

A 1986 quasi-experimental study involving 17 people recorded transient amenorrhoea.

A 1986 cohort study involving 10 people recorded decreases in serum potassium, sodium, and iron.

A 2025 cross-sectional study involving 384 people recorded dizziness.

A 2025 cross-sectional study involving 384 people recorded nausea.

A 2025 cross-sectional study involving 384 people recorded panic-like symptoms.

A 1989 case report described acute corneal swelling in both eyes, with breaks in the Descemet's membrane and marked swelling in the back of the cornea; penetrating keratoplasty was required.

A 1985 randomized trial involving 6 people found a lowered insulin response (P less than 0.001) to a glucose challenge during heating compared with an oral glucose tolerance test under thermoneutral conditions (23 degrees C). This finding describes the insulin response, not a measured increase in blood glucose.

Pharmacology references note that fluid loss, vasodilation, and heat strain may cause transient generalized weakness, particularly after prolonged sessions.

Sweating-related fluid loss can cause transient dry mouth and thirst after sauna use.

Pharmacology references note that heavy sweating and volume or electrolyte loss can precipitate transient muscle cramps during or after sauna exposure.

Severe dehydration from prolonged or frequent sauna use without rehydration can reduce renal perfusion and temporarily impair kidney function.

Pharmacology references describe heat exposure, dehydration, and temporary blood-pressure changes as possible causes of headache during or after sauna use. Some people also reported this effect in community posts.

Pharmacology references describe a potential risk for people who use injected insulin: sauna heat can increase skin blood flow and speed insulin absorption, which can cause low blood sugar.

Heat strain and sweat-related fluid loss can raise core temperature and leave people drowsy and mentally tired for some hours after a session.

Pharmacology references describe how sauna heat raises heart rate and sympathetic drive, while heavy sweating can lead to fluid and potassium loss; these changes can trigger extra beats or an irregular rhythm, mainly in people with heart disease or after alcohol or a cold plunge.

Pharmacology references note that severe overheating and dehydration, especially after hard exercise or with alcohol, can damage muscle cells (rhabdomyolysis); this is rare with normal sauna use.

Slipping on wet floors or falling because of heat-related dizziness when leaving the sauna can cause sprains and muscle strains.

Diabetic autonomic neuropathy can impair sweating and blood-pressure regulation, increasing the risk of heat intolerance and low blood pressure during sauna use.

In a quasi-experimental study of 45 considerably overweight men, 40-minute sauna sessions were described as potentially excessive and dangerous; by the fourth session, average blood pressure reached 140/94 mmHg and heart rate reached difficult or maximal-effort ranges. A separate cross-sectional study of 674 people linked high BMI with greater inferred risk of dehydration, but did not measure dehydration as an adverse outcome.

A randomized controlled trial in 8 insulin-treated people with diabetes found that sauna lowered blood glucose, attributed to faster insulin absorption, suggesting a risk of low blood glucose for this group.

An active fever already raises core temperature and bodily stress; additional sauna heat may worsen overheating, dehydration and cardiovascular strain.

During active heat stroke or incomplete recovery from a recent heat illness, impaired heat regulation can make further heat exposure potentially life-threatening.

Sauna heat widens peripheral blood vessels, which may lower already-low blood pressure further and lead to marked dizziness, reduced blood flow to the brain or fainting.

When standing or leaving the sauna, impaired blood-pressure compensation combined with heat-related blood-vessel widening may cause near-fainting or fainting.

The concern is that maternal core temperature above 39°C, especially early in pregnancy, increases the risk of neural tube defects; sauna heat can rapidly raise core temperature to this level.

Diarrhea can cause fluid loss before sauna exposure, while sweating may further worsen dehydration, low blood pressure and electrolyte disturbance.

Sauna-related overheating may lower the seizure threshold and trigger seizures in susceptible people.

In the first weeks after a stroke, unstable autonomic control and blood-pressure fluctuations may make the cardiovascular stress of sauna use dangerous.

Open or contagious skin lesions may spread infection in the warm, humid sauna environment, and heat exposure may worsen them.

Heavy sweating can reduce body water and kidney excretion of uric acid, raising blood uric acid and potentially triggering a gout flare. A pharmacology reference specifically notes an additive rise in plasma uric acid when beer is consumed after sauna bathing; its recommendation concerns that combination.

A review states that people with unstable angina should strictly avoid sauna use because it may increase the heart’s oxygen demand. The broader link between angina and sauna use is described as a possible contraindication, but further evidence is needed to establish it.

Reviews describe sauna use after a recent heart attack as an absolute contraindication unless a cardiologist specifically clears it; potential blood-pressure fluctuations are a concern.

A review lists urticaria among the skin conditions warranting caution with sauna use.

A review advises caution because sauna-related blood-pressure fluctuations may be a concern for people with Heart Valve Disease.

Heat stress increases the demand for a cortisol response; limited adrenal reserve may raise the risk of circulatory collapse or adrenal crisis.

Sweating-related dehydration may increase blood viscosity and potentially precipitate a sickle cell crisis.

Sweating-related fluid and electrolyte shifts may lead to low blood pressure and high potassium in people receiving dialysis.

Reduced heat regulation and cardiovascular reserve in frail older adults may increase the risk of heat stroke and low blood pressure.

Excess thyroid hormone increases heat production, and sauna heat may worsen a fast heart rate or precipitate thyroid storm.

Heat stress may trigger catecholamine release from the tumor, potentially causing a hypertensive crisis or abnormal heart rhythms.