I have a fever. Can I use the sauna?

Don't, and don't take our word for why. Take it to a doctor. There's no research on sauna during a fever and there never will be. What's known is that a fever is a raised set point your body is defending on purpose, that heat has been reported to drop systolic blood pressure by roughly 11 to 27 mmHg within 24 hours, and that a raised body temperature already lifts your heart rate and oxygen consumption by itself. No one has put those together and measured it. And if you've taken paracetamol or ibuprofen in the last few hours, a normal reading on the thermometer isn't the answer to this question.

Does sweating out a cold work?

It's been tested about as directly as a folk remedy ever gets tested, and no. A randomized trial in Berlin put 157 people with fresh colds in a 90°C sauna — both groups, in winter coats, three minutes — and tested one thing only: whether breathing the sauna's hot air through a mask helped. It didn't. A larger trial pumped 41°C air into 170 people's noses two hours a day for five days and found nothing on severity or duration. Cochrane pooled six trials and 387 people on a medical device that pipes heated humid air up your nose — not a sauna — and found neither benefit nor harm from that device. A normal session has never been tested.

I've got a mild head cold and I feel fine. Am I allowed in?

We don't screen anyone at the door, so it's your call rather than ours. Make it with the real information. The sauna won't fix your cold; that's the one thing the evidence is clear about. Whether it might hurt is genuinely unknown, because a normal session on someone with a cold has never been tested. And you'd be sharing a small room. We'd rather you rebooked, and memberships pause without penalty. If you go in regardless, the get-out list above is shorter for you than for everyone else — light-headedness on standing especially.

Will regular sauna stop me catching colds in the first place?

Maybe, and that's a different question from this one. It also holds the only positive evidence in the field: a 1990 controlled trial in which 25 sauna bathers caught fewer colds over six months than 25 people who abstained. Fifty people, unreplicated in thirty-six years, and Ernst himself only claimed "probably." Whatever that's worth, it's about not catching one — the same paper found no difference in how long colds lasted or how bad they got.

Is the flu different from a cold here?

That's above our pay grade, and it's also genuinely unanswered. The best-powered trial in this area excluded anyone who tested positive for influenza by design, and its authors wrote that "investigation of rNHF in the treatment of influenza is warranted." It hasn't been done. Fever, or anything in your chest — that isn't a call for a sauna studio to make.

What about the cold plunge while I'm sick?

Untested. There isn't a study and we won't invent one. What's documented is that cold shock is involuntary — a gasp, a jump in blood pressure, hyperventilation — and that those responses "override both conscious and other autonomic respiratory controls." That research is drowning and survival work in healthy people, usually submerged, usually in colder water than ours. Whether an infection makes it worse, nobody knows. The plunge is optional and it isn't going anywhere.

Can You Use a Sauna When You're Sick?

Not with a fever, and not with anything in your chest — that one's for a doctor. Somebody did run the trial: 157 people with fresh colds, breathing 90°C sauna air through a mask. Read the methods before you cite the result. They wore winter coats and stayed three minutes.

No. Not with a fever, and not with anything that's moved into your chest. Those are doctor's questions and we're not qualified to answer them. Not if you've been throwing up or running to the bathroom either — that one isn't about the virus, it's about the fluid. You're already down, and 90 minutes at 180 to 200°F takes more. And if you've taken paracetamol or ibuprofen in the last few hours, the thermometer isn't the thing to ask. Sick enough to be dosing yourself is the same answer as having a fever.

If you have a head cold and you feel basically functional, the honest answer is more awkward. The sauna is very unlikely to do anything for it, a normal session has never been tested on someone with a cold, and there'll be other people in the room. We'd rather you rebooked. Memberships pause without penalty.

Sweating out a cold is one of the oldest ideas in the folk medicine cabinet. Unlike most of them, it has been checked. An empty booking costs us money, so read the rest with that in mind.

Somebody ran this trial in a real sauna

Berlin, across the winters of 2007 to 2009. Researchers randomized 157 people who had just come down with a common cold and sent them into a sauna at 90°C, about 195°F. Eighty of them breathed the sauna's own hot dry air through a mouth mask. The other 77 breathed 24°C outside air through the same kind of mask.

The result was nothing. Symptom severity summed across days 2, 3, 5 and 7 came in at 31.2 against 35.1 for the control — a difference of -3.9, on a confidence interval running from -9.7 to 1.9. Straight through zero. The authors' conclusion, word for word: "Inhaling hot air while in a sauna has no significant impact on overall symptom severity of the common cold."

Read the methods, though. Both groups sat in the 90°C room. Both wore winter coats, and the paper specifies the fabric: 63% acrylic, 37% polyester, 1.5 cm thick. Both stayed roughly three minutes, on three consecutive days. That was deliberate — the authors wanted "the short stay and the insulation provided by the winter coat should avoid circulatory imbalance and sweating." They engineered the sauna out of the sauna so they could test the air by itself.

Three minutes in a parka is not a session, and there was no non-sauna arm at all. The only contrast was inhaled hot air against inhaled room-temperature air. Notice "overall" in that conclusion, too. The authors put it there because three secondary outcomes did clear the significance line while the primary sat null. They scoped their own claim. We won't sell you those three as a benefit.

The longer exposure did nothing either

If three minutes of hot air is too small a dose, somebody ran a much longer one. New Zealand, 170 people with colds, caught within 48 hours of their first symptom. A machine pushed fully humidified 41°C air into their noses at 35 litres a minute, two hours a day, for five days. Day-four symptom scores came in at 6.33 against 5.80 for the sham, and the colds lasted the same. Nothing.

That's a medical device aimed at the nose, not a sauna. And here's the part the authors insist on that nobody quoting them repeats: 41°C may not have been hot enough. They picked it as a safety ceiling rather than a maximum, because nasal burns are reported at 43°C. They also concede the nose may never have reached even that, listing among the explanations for their own null that "the temperature of the inspired gas in the nasopharynx was cooler than the 41°C delivered by the device." So it's the largest dose anyone could safely run, and it failed.

What it has going for it is duration: ten hours of heated air up the nose across five days, against the few minutes a sauna round puts there. Our reasoning, not the paper's — if airway heat were the lever, ten hours should have found it. One prespecified subgroup cuts against us rather than for us, so it belongs here: among the people who actually had rhinovirus, the heated-air group did worse than the sham.

Cochrane pooled six trials and 387 people in 2017. Verbatim: "The current evidence does not show any benefits or harms from the use of heated, humidified air delivered via the RhinoTherm device for the treatment of the common cold." A verdict on one device, not on hot air in general. Even the narrow question has no clean answer — graded low quality, and the reviewers concede either analysis method is defensible, so run the numbers one way and an effect appears, run them the other and it vanishes.

The study everyone cites says the opposite of what they think

There is one study that appears to show sauna beating colds. It does not show that.

Ernst and colleagues, 1990. Twenty-five volunteers bathing regularly against 25 abstaining, colds logged for six months. The sauna group caught fewer, "found particularly during the last three months of the study period when the incidence was roughly halved compared to controls." That's the sentence people quote.

Here's the next one, verbatim: "The mean duration and average severity of common colds did not differ significantly between the groups." The paper produced to prove sauna helps once you're sick is the paper that went looking and came back empty-handed. Catching fewer colds and shortening the one you have are separate claims.

Hold even that loosely. Fifty people split in half, which makes the null on duration a failure to detect an effect rather than proof there isn't one. PubMed indexes it as a controlled clinical trial rather than a randomized one, and we couldn't read the methods to check how people were allocated. Ernst's own conclusion was hedged to the floor: regular sauna "probably reduces the incidence of common colds, but further studies are needed to prove this." That was thirty-six years ago. We went looking for the replication and didn't find one.

"Heat kills the virus" is a mouse experiment about your nose

The mechanism people reach for is real. It just isn't about saunas.

Foxman and colleagues, 2015, took mouse airway cells — cells in a dish, not mice with colds — and infected them with a mouse-adapted rhinovirus. At 33°C, roughly the temperature inside your nose, the virus replicated better than it did at 37°C, your core body temperature, where the cells mounted a stronger interferon response.

Read those two numbers again. The warm arm of that experiment is normal body temperature. You are already running it. The finding is that a cool nose is a more hospitable nose for rhinovirus, which is a fact about noses rather than an argument for a hot room. Nothing shows a sauna raises the lining of your nose to a temperature that kills anything, and both trials built to test the idea on a human with an actual cold came back null.

A fever is not a thermostat that broke

The other argument runs that a sauna is an artificial fever, so it should do what a fever does. That has the physiology backwards.

Fever and hyperthermia are separate entities. Fischler and Reinhart put it plainly: fever "develops when cytokines increase the thermostatic set point in the hypothalamus," whereas "Hyperthermia is a distinct entity in which the thermostatic set point is normal but the heat control mechanism fails." A fever is your thermostat moved on purpose. A sauna is heat forced against a thermostat that hasn't moved.

And the fever isn't a malfunction to be helped along. Evans and colleagues describe it as "a cardinal response to infection" conserved across vertebrates "for more than 600 million years of evolution," one that "confers a survival benefit during infection." It's an expensive program your body is running deliberately. Nobody has shown external heat tops it up, or that the body has any use for it while that program runs.

Raised temperature already costs you. Fischler and Reinhart list the debit side of a raised body temperature as "increased heart rate, oxygen consumption and metabolism." Set that beside what heat does to blood pressure: a 2026 review across saunas, hot springs, hot water immersion and mudpacks reported systolic drops of roughly 11 to 27 mmHg within 24 hours. From the same review, on how well any of this is understood: "Serious acute adverse events were rare, but few studies specifically targeted adults aged ≥65 years or systematically reported comorbidities and background antihypertensive therapy."

Here's the part you won't read on other sauna websites. A sauna during a fever has never been studied. Not one trial, and there never will be one — no ethics committee is going to approve heating febrile people to 195°F to find out. The case against it is two verified facts placed next to each other and reasoned across, which is not evidence. That's a reason for caution, not a reason for confidence in either direction.

Don't let the general safety literature stand in as clearance, either. It says healthy. Kukkonen-Harjula and Kauppinen: "Sauna was well tolerated and posed no health risks to healthy people from childhood to old age." Then, in the same review: "The research data retrieved were most often based on uncontrolled research designs with subjects accustomed to bathing since childhood." Every reassuring line in that literature is scoped to healthy bathers or people with stable chronic conditions. Acute infection isn't addressed anywhere in it. Silence isn't a green light.

That review has exactly one line on drugs, and it's narrow: medication generally wasn't a concern during a bath, "apart from antihypertensive medication, which may predispose to orthostatic hypotension after bathing." Worth holding next to an 11-to-27 mmHg drop. What the cold-and-flu aisle does in a hot room, nobody has looked at. If you're taking something for it, ask a pharmacist rather than us.

Pregnant and sick is two questions at once and we're not qualified for either. The sauna literature that mentions pregnancy at all is talking about healthy pregnancies, which isn't the situation you're asking about. Same goes for the hard stops that 2001 review in The American Journal of Medicine names: unstable angina, a recent heart attack, severe aortic stenosis. None of them are ours to rule on.

The cold is a separate unknown

Cold shock isn't a feeling, it's a reflex: "an initial gasp, hypertension, and hyperventilation despite a profound hypocapnia." Those responses "override both conscious and other autonomic respiratory controls." You don't decide to gasp.

A companion paper notes that cold water submersion "can induce a high incidence of cardiac arrhythmias in healthy volunteers" and proposes a clash of sympathetic and parasympathetic drive as the cause. Note the authors' own verbs, "we propose" and "we also hypothesise" — a mechanism on offer, not a settled fact. Note who it happened to, as well: healthy volunteers, in drowning and survival research, usually colder water, usually head under. Our plunges run 45 to 55°F, head out, in a staffed room. What an active infection does to any of it has never been measured.

You'd be sharing the room

A sauna is a small enclosed space with other people breathing in it. Respiratory viruses ride aerosols thrown off by ordinary breathing and talking, and a 2021 review in Science argues they stay suspended and get inhaled, and that the old droplet-versus-airborne split doesn't describe how transmission actually works. Viral transmission in a sauna has never been measured, and neither has what 180 to 200°F air does to a virus floating in it, or what changes when someone ladles water onto the stones. We won't tell you the heat sterilizes the room, and we won't tell you it doesn't. The other people booked into that hour didn't book a cold.

If you go in anyway

We don't screen anyone at the door, and some of you will read all of that and book regardless. So here's the get-out list, and it's shorter for you than for everyone else. Leave at the first one, and don't negotiate with yourself about it.

No alcohol, ever. A Swedish autopsy series — 77 sauna deaths across twelve years — found alcohol in 71% of those tested, running higher than the Finnish figure we cite elsewhere on this site. The clinical review is explicit that it "increases the risk of hypotension, arrhythmia, and sudden death, and should be avoided."

Don't bathe alone either. In that same series, of the people found dead in a sauna, all but two were found on their own, and the authors' recommendation is that bathing alone "is a risk factor that can easily be avoided." A case series with no denominator can't produce a rate, only a profile. It carries more weight if you're unwell, because someone unwell is likelier to feel faint — which cuts against the private suite. It's the one room where nobody would notice, so on a day you're not right that's a reason to skip it rather than a reason to book it.

Fluid, too, and this one is reasoning rather than a finding. Being ill tends to cost you some. A sauna definitely costs more.

Dizziness or light-headedness, especially on standing
Headache
Nausea
Your heart pounding in a way that feels wrong rather than warm
Chills, or sweating that shuts off
Confusion, or losing the thread of a conversation

Common questions

I have a fever. Can I use the sauna?: Don't, and don't take our word for why. Take it to a doctor. There's no research on sauna during a fever and there never will be. What's known is that a fever is a raised set point your body is defending on purpose, that heat has been reported to drop systolic blood pressure by roughly 11 to 27 mmHg within 24 hours, and that a raised body temperature already lifts your heart rate and oxygen consumption by itself. No one has put those together and measured it. And if you've taken paracetamol or ibuprofen in the last few hours, a normal reading on the thermometer isn't the answer to this question.
Does sweating out a cold work?: It's been tested about as directly as a folk remedy ever gets tested, and no. A randomized trial in Berlin put 157 people with fresh colds in a 90°C sauna — both groups, in winter coats, three minutes — and tested one thing only: whether breathing the sauna's hot air through a mask helped. It didn't. A larger trial pumped 41°C air into 170 people's noses two hours a day for five days and found nothing on severity or duration. Cochrane pooled six trials and 387 people on a medical device that pipes heated humid air up your nose — not a sauna — and found neither benefit nor harm from that device. A normal session has never been tested.
I've got a mild head cold and I feel fine. Am I allowed in?: We don't screen anyone at the door, so it's your call rather than ours. Make it with the real information. The sauna won't fix your cold; that's the one thing the evidence is clear about. Whether it might hurt is genuinely unknown, because a normal session on someone with a cold has never been tested. And you'd be sharing a small room. We'd rather you rebooked, and memberships pause without penalty. If you go in regardless, the get-out list above is shorter for you than for everyone else — light-headedness on standing especially.
Will regular sauna stop me catching colds in the first place?: Maybe, and that's a different question from this one. It also holds the only positive evidence in the field: a 1990 controlled trial in which 25 sauna bathers caught fewer colds over six months than 25 people who abstained. Fifty people, unreplicated in thirty-six years, and Ernst himself only claimed "probably." Whatever that's worth, it's about not catching one — the same paper found no difference in how long colds lasted or how bad they got.
Is the flu different from a cold here?: That's above our pay grade, and it's also genuinely unanswered. The best-powered trial in this area excluded anyone who tested positive for influenza by design, and its authors wrote that "investigation of rNHF in the treatment of influenza is warranted." It hasn't been done. Fever, or anything in your chest — that isn't a call for a sauna studio to make.
What about the cold plunge while I'm sick?: Untested. There isn't a study and we won't invent one. What's documented is that cold shock is involuntary — a gasp, a jump in blood pressure, hyperventilation — and that those responses "override both conscious and other autonomic respiratory controls." That research is drowning and survival work in healthy people, usually submerged, usually in colder water than ours. Whether an infection makes it worse, nobody knows. The plunge is optional and it isn't going anywhere.

Sources

Every number on this page traces to one of these. Where the research is thin or a popular claim is oversold, we say so above.

Pach D, Knöchel B, Lüdtke R, Wruck K, Willich SN, Witt CM. "Visiting a sauna: does inhaling hot dry air reduce common cold symptoms? A randomised controlled trial." Medical Journal of Australia, 2010;193(11-12):730-4 (PMID 21143077). — The most directly on-topic trial that exists. Single-blind RCT, 157 people with a newly acquired common cold, run at a sauna in Berlin Nov 2007–Mar 2008 and Sep 2008–Apr 2009. Intervention (n=80) inhaled the hot dry sauna air through the mouth via a mask; control (n=77) inhaled dry air from outside the sauna (24°C) through the mouth via a mask. Primary outcome (AUC of symptom severity across days 2/3/5/7) was null: 31.2 (SEM 1.8) vs 35.1 (SEM 2.3), difference -3.9 (95% CI -9.7 to 1.9), p=0.19. Authors' conclusion, verified verbatim against the PubMed record and the MJA text: "Inhaling hot air while in a sauna has no significant impact on overall symptom severity of the common cold." Note the exact wording — no "dry" in the conclusion, and "overall" is load-bearing, because three secondary outcomes DID reach p<0.05 (medication use day 1, p=0.01; severity day 2, p=0.04; participants' rating day 7, p=0.03) against a null primary and multiple comparisons. Not reported on the page as a benefit. CRITICAL SCOPE LIMIT: both arms sat in the same 90°C / 20%-humidity sauna in winter coats (63% acrylic, 37% polyester, 1.5 cm thick) for about 3 minutes on 3 consecutive days, because "the short stay and the insulation provided by the winter coat should avoid circulatory imbalance and sweating." There was NO non-sauna comparator. It isolates inhaled hot air; it is NOT a test of a normal sauna session. The 20% humidity figure describes THIS Berlin study sauna and is not a Sauna Culture operating spec — it is not applied to our room anywhere on this page.
Bird G, Braithwaite I, Harper J, et al. "Rhinothermy delivered by nasal high flow therapy in the treatment of the common cold: a randomised controlled trial." BMJ Open, 2021;11(11):e047760 (PMID 34848508). — The best-powered human test of heating the airway to beat a cold. Single-blind parallel-group RCT, New Zealand, 170 participants aged 18-75 (mean 27.5, predominantly university students), recruited within 48h of symptom onset, Modified Jackson Score ≥7, influenza-negative by point-of-care test. Intervention (n=85): 100% humidified air at 41°C, 35 L/min, 2 hours daily for 5 days. Sham (n=85): 31°C, 10 L/min, 10 min daily. Day-4 MJS 6.33 (SD 3.97) vs 5.80 (SD 3.15), difference 0.37 (95% CI -0.69 to 1.42), p=0.49. Time to resolution 5.96 (4.47) vs 6.42 (4.09) days, p=0.91. Conclusion verbatim: "This well-powered, single-blind randomised controlled trial does not provide evidence that 5 days of rNHF... reduces common cold symptom severity or duration. However, investigation of rNHF in the treatment of influenza is warranted." AUTHORS' OWN DOSING CAVEAT, verified in the discussion and load-bearing on this page: a stated potential explanation for the lack of efficacy is that "the temperature of the inspired gas in the nasopharynx was cooler than the 41°C delivered by the device, or a temperature higher than 41°C is required to inhibit viral replication"; they "selected 41°C to ensure that airway temperature did not exceed 42°C" because regulatory guidance caps inspired air at 42°C and minor nasal mucosal burns are reported at 43°C. So this is a safety-ceilinged dose, not a maximal one. The same discussion notes "clinical evidence that temperatures >41°C may be required to elicit a benefit in vivo, based on studies which have shown improvement in common cold symptoms with delivery of HHA at 42°C–44°C" — which is why this page does NOT claim airway heating is null in every human test. PRESPECIFIED SUBGROUP: rhinovirus status was a prespecified effect modifier; HRV-positive participants did WORSE on rNHF than sham, difference 2.07 (95% CI 0.41 to 3.73), p=0.015, p-interaction=0.001. Reported on the page as a subgroup only, with nothing built on it. SCOPE: a medical device delivering heat to the nose, not a sauna.
Singh M, Singh M, Jaiswal N, Chauhan A. "Heated, humidified air for the common cold." Cochrane Database of Systematic Reviews, 2017;8(8):CD001728 (PMID 28849871). — Systematic-review-level verdict. 6 trials from 5 publications, 387 participants. Conclusion quoted IN FULL on the page, verbatim: "The current evidence does not show any benefits or harms from the use of heated, humidified air delivered via the RhinoTherm device for the treatment of the common cold." The device clause is not optional — truncating it would inflate a one-device null into a verdict on heated humid air in general, which the review cannot support. Evidence graded LOW quality for significant heterogeneity. The result is model-dependent and the review says so: fixed-effect OR 0.30 (95% CI 0.16-0.56; 2 studies, 149 participants) vs random-effects OR 0.22 (95% CI 0.03-1.95), with the reviewers noting "There is an argument for using either form of analysis." Because the fixed-effect analysis DOES show an effect, this page does not claim airway heating has been null in every human test. Viral shedding in nasal washings: OR 0.47 (95% CI 0.04-5.19), not significant. Participants reporting resolution: OR 0.58 (95% CI 0.28-1.18), not significant. One US study showed worsened nasal resistance, an earlier Israeli study improvement. Also the cleanest source for the folk belief's stated rationale — that steam may help mucus drain and heat may destroy the virus as it does in vitro — presented by the review as theoretical basis, not finding. SCOPE: RhinoTherm device, not a sauna; risk of bias unclear for randomisation.
Ernst E, Pecho E, Wirz P, Saradeth T. "Regular sauna bathing and the incidence of common colds." Annals of Medicine, 1990;22(4):225-7 (PMID 2248758). — The study everyone cites for sauna-when-sick, and it does not support that claim. 25 volunteers sauna-bathing vs 25 abstaining from this or comparable procedures; frequency, duration and severity of colds recorded for 6 months. Significantly fewer episodes in the sauna group, "found particularly during the last three months of the study period when the incidence was roughly halved compared to controls." The decisive sentence, verbatim: "The mean duration and average severity of common colds did not differ significantly between the groups." So it is a PREVENTION finding in healthy people and a null on duration and severity once a cold exists. PRECISION ON THE NULL: with 50 people total this is a failure to detect an effect, not a demonstration that no effect exists — the page states it that way and does not round the null down into a finding. Authors' hedged conclusion verbatim: "It is concluded that regular sauna bathing probably reduces the incidence of common colds, but further studies are needed to prove this." LIMITATIONS: n=50 total; blinding impossible; 36 years old; no replication found. PRECISION: PubMed indexes the publication types as "Clinical Trial" and "Controlled Clinical Trial," NOT "Randomized Controlled Trial," and the full text was not accessible to confirm allocation — described on the page as a controlled trial only.
Foxman EF, Storer JA, Fitzgerald ME, et al. "Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells." Proceedings of the National Academy of Sciences, 2015;112(3):827-32 (PMID 25561542). — The actual science under "heat fights the cold virus," and far narrower than the folk claim. Primary MOUSE airway epithelial cells IN CULTURE — cells in a dish — infected with mouse-adapted rhinovirus 1B. No live mouse in this paper ever had a cold, so it is a single tier of evidence, not two; the page says "a dish of mouse cells" for that reason. The comparison is 33°C (the cool temperature of the nasal cavity) against 37°C (CORE BODY TEMPERATURE) — a 4°C difference at the mucosa. At 37°C cells showed "a striking enrichment in expression of antiviral defense response genes," with higher type I and type III IFN and ISG expression; virus replicated better at 33°C. Effect was MAVS- and type-I-IFN-receptor-dependent. WHAT IT IS NOT: not a sauna study, not a human study, and the warm comparator is normal body temperature rather than hot air. Supports "a cool nose is a more hospitable nose for rhinovirus," not "sit in a hot room."
Fischler MP, Reinhart WH. "[Fever: friend or enemy?]" Schweizerische Medizinische Wochenschrift, 1997;127(20):864-70 (PMID 9289813). German language, English abstract. — The cleanest statement of the fever/hyperthermia distinction, which is the physiological spine of this page. Verbatim from the English abstract: "Fever develops when cytokines increase the thermostatic set point in the hypothalamus, which in turn results in increased body temperature via increased heat production and decreased heat dissipation. Hyperthermia is a distinct entity in which the thermostatic set point is normal but the heat control mechanism fails." ATTRIBUTION PRECISION: the costs are attributed by the authors to RAISED BODY TEMPERATURE generally, not to fever specifically — "Increased body temperature has positive effects (e.g. decreased bacterial growth, stimulation of host defence mechanisms) as well as negative effects (e.g. increased heart rate, oxygen consumption and metabolism)." The page words it that way. Concludes that whether fever is friend or foe "depends on the actual clinical circumstances." HEAVY LIMITATIONS: 1997; narrative review with no primary data; full text is in German and only the English abstract was verified. Cited for the concept only — no number on this page is attached to it, and it says nothing about saunas.
Evans SS, Repasky EA, Fisher DT. "Fever and the thermal regulation of immunity: the immune system feels the heat." Nature Reviews Immunology, 2015;15(6):335-49 (PMID 25976513). — Narrative review, no primary data. Establishes that fever is not a malfunction: "Fever is a cardinal response to infection that has been conserved in warm-blooded and cold-blooded vertebrates for more than 600 million years of evolution. The fever response is executed by integrated physiological and neuronal circuitry and confers a survival benefit during infection." Cited only for the point that a febrile body is already running a deliberate, coordinated, expensive defence programme. It says nothing about sauna and does NOT support any inference that external heat adds to, substitutes for, or amplifies fever's benefit — if anything it cuts the other way, since fever is regulated and a sauna is not part of that regulation.
Yamasaki S, Tokunou T, Kashiwado Y, Makishi M, Horiuchi T. "Acute blood pressure responses and safety considerations in heat therapy interventions: A narrative review." Complementary Therapies in Medicine, 2026;98:103341 (PMID 41794190). — Narrative review, databases searched to 13 March 2024; 2 RCTs, 1 crossover, 7 non-randomised interventional and 11 observational studies, participants aged 18-94. Across saunas, mineral hot spring bathing, hot water immersion and mudpack therapy, systolic BP reductions of approximately 11-27 mmHg within 24 hours were REPORTED — the page carries the "reported" and the "within 24 hours" in both the body and the FAQ, because most included studies "lacked control groups and showed marked heterogeneity in populations, temperatures, timing of exposure, and outcome assessment." The load-bearing honesty, verbatim: "Serious acute adverse events were rare, but few studies specifically targeted adults aged ≥ 65 years or systematically reported comorbidities and background antihypertensive therapy," and "The long-term antihypertensive efficacy of heat therapy is unproven, and safety margins in frail older adults and beta-blocker users remain insufficiently defined." NOT about illness — cited for the BP-drop mechanism and for where the heat-safety evidence has holes.
Kukkonen-Harjula K, Kauppinen K. "Health effects and risks of sauna bathing." International Journal of Circumpolar Health, 2006;65(3):195-205 (PMID 16871826). — Literature review covering sauna experiments at 80-90°C, 5-20 minute exposures repeated 1-3 times. The reassuring line, verbatim: "Sauna was well tolerated and posed no health risks to healthy people from childhood to old age." The MEDICATION line, verbatim, which this page uses because a person with a cold is by default a medicated person: "Medication in general was of no concern during a bath, apart from antihypertensive medication, which may predispose to orthostatic hypotension after bathing." Also: not particularly risky for medicated, stable hypertension / coronary heart disease / congestive heart failure patients; and "Excepting toxemia cases, no adverse effects of bathing during pregnancy were found" — scoped to healthy pregnancies, which is why this page routes pregnancy to a doctor rather than importing the reassurance. The most valuable part is the self-criticism, verbatim: "The research data retrieved were most often based on uncontrolled research designs with subjects accustomed to bathing since childhood," and further research is needed "with subjects not accustomed to sauna." The "healthy people" and "accustomed since childhood" qualifiers are load-bearing, and the review is silent on acute illness — so it clears nobody who is sick.
Hannuksela ML, Ellahham S. "Benefits and risks of sauna bathing." The American Journal of Medicine, 2001;110(2):118-26 (PMID 11165553). — Narrative review; the standard source for named contraindications. Verbatim: "Contraindications to sauna bathing include unstable angina pectoris, recent myocardial infarction, and severe aortic stenosis." And verbatim: "alcohol consumption during sauna bathing increases the risk of hypotension, arrhythmia, and sudden death, and should be avoided." Also states that very few acute myocardial infarctions and sudden deaths occur in saunas, that sauna is well tolerated by most healthy adults and children, and that it is safe during uncomplicated pregnancies of healthy women. CRITICAL SCOPE LIMIT: every reassuring statement in this review concerns HEALTHY people or people with STABLE chronic conditions. It does not address acute infection or fever at all and is not cited here as clearance to sauna while sick. 25 years old; narrative, not systematic; no pooled data.
Datta A, Tipton M. "Respiratory responses to cold water immersion: neural pathways, interactions, and clinical consequences awake and asleep." Journal of Applied Physiology, 2006;100(6):2057-64 (PMID 16714416). — Review with original data; the canonical description of cold shock, verbatim: "A fall in skin temperature elicits a powerful cardiorespiratory response, termed 'cold shock,' comprising an initial gasp, hypertension, and hyperventilation despite a profound hypocapnia." The sentence that matters most for a plunge page, verbatim: "The respiratory responses to skin cooling override both conscious and other autonomic respiratory controls and may act as a precursor to drowning." Also notes "emerging evidence" that post-apnea respiratory rhythm, hypoxemia and coincident sympathetic and cyclic vagal stimulation may be an arrhythmogenic trigger — the authors are hedging there. SCOPE LIMITS: built on cold-water immersion, survival and drowning research, typically colder water and often whole-body or head submersion. Not a study of a supervised 45-55°F head-out plunge, and silent on doing so while infected. Establishes mechanism and direction, not magnitude of risk in a studio plunge.
Shattock MJ, Tipton MJ. "'Autonomic conflict': a different way to die during cold water immersion?" The Journal of Physiology, 2012;590(14):3219-30 (PMID 22547634). — Review / hypothesis paper. Verbatim: "Cold water submersion can induce a high incidence of cardiac arrhythmias in healthy volunteers." Proposes that cold shock (sympathetic tachycardia) and the diving response (parasympathetic bradycardia) fire simultaneously: "We propose that the strong and simultaneous activation of the two limbs of the autonomic nervous system ('autonomic conflict') may account for these arrhythmias and may, in some vulnerable individuals, be responsible for deaths that have previously wrongly been ascribed to drowning or hypothermia." CRITICAL: the authors' own verbs are "we propose" and "we also hypothesise" — a proposed mechanism, not settled fact, and not stated as established on this page. Concerns submersion with breath-holding; not demonstrated for head-out plunging, and nothing in it addresses infection. The arrhythmias were in healthy volunteers.
Wang CC, Prather KA, Sznitman J, Jimenez JL, Lakdawala SS, Tufekci Z, Marr LC. "Airborne transmission of respiratory viruses." Science, 2021;373(6558):eabd9149 (PMID 34446582). — Major review in Science. Establishes that virus-laden aerosols are generated by ordinary breathing and talking, are transported and remain suspended in air, and are inhaled, and that the traditional dichotomy is wrong: "The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection." Cited for the general principle only: a shared enclosed room with other people in it is a transmission setting. HARD LIMIT: this paper says nothing about saunas. Nobody has measured viral transmission in a sauna, and whether 180-200°F air changes aerosol viability in that room is not addressed here and is not established in either direction — so this page claims neither. No humidity figure is asserted for our room anywhere on this page: this is a löyly sauna where bathers pour water on the stones, so humidity is not a stable house number and we have not measured it.
Rodhe A, Eriksson A. "Sauna deaths in Sweden, 1992-2003." American Journal of Forensic Medicine and Pathology, 2008;29(1):27-31 (PMID 19749613). — Case series drawn from a national database of all Swedish medicolegal autopsies 1992-2003 — TWELVE years inclusive, as the paper's own title states; 77 sauna-related deaths. 82% men, most middle-aged; 84% found dead in the sauna. Blood alcohol was determined in 69 cases and 49 (71%) tested positive, "often with high concentrations." Of 65 cases with an identifiable major disease or state, 34 (44%) were alcohol-related and 18 (23%) cardiovascular. The most actionable line, verbatim: "Among the cases found dead in a sauna, all but 2 were found alone. Obviously, bathing alone is a risk factor that can easily be avoided and should perhaps be emphasized more." HARD LIMITATION: case series with NO DENOMINATOR — it cannot produce a rate or a per-session risk, only the profile of people who died. Does not mention illness or fever anywhere. NOTE ON THE 71%: this is the Swedish series and is a different study from the Finnish Kenttämies & Karkola 2008 series (50% alcohol) cited on other pages of this site. The page names the country and flags that the two figures differ, so the numbers cannot read as a site inconsistency. The Swedish series is used here because it is the one that supports the bathing-alone point.

Nobody takes your temperature at the desk. That's exactly why we'd rather hand you the evidence than a comfortable answer — the call is yours, and there's no one at the door to make it for you. If you're running a fever, call your doctor. The room will still be hot next week.

How Often Should You Use the Sauna?Traditional Finnish Sauna The Sauna Culture — Visitor Handbook