Infrared Sauna

Waon therapy in Japan

A 1995 study from Kagoshima University by Tei and colleagues examined thermal vasodilation in 34 patients with chronic congestive heart failure. Patients took either a warm-water bath for 10 minutes at 41°C or a sauna bath for 15 minutes at 60°C while intracardiac pressures were recorded. The authors noted that such baths had generally been considered inappropriate for severe heart failure, and concluded that thermal vasodilation could be applied with little risk if appropriately performed.

The name Waon therapy appears in later papers. A 2010 review by Miyata and Tei describes it as thermal treatment in a dry sauna kept at 60°C that differs from the traditional sauna, and a 2015 paper by Tei's group states that they developed it using a far-infrared dry sauna. A 2016 trial report calls it a holistic soothing warmth therapy. The sources reviewed give no date for the first use of the name and no etymology for it.

Far-infrared heating in saunas

A 2012 narrative review by Vatansever and Hamblin defines far infrared as wavelengths of 3 to 100 micrometers and states that saunas delivering far-infrared radiation have become widely used. The review's description of these devices as safe and effective is the authors' own characterization. A 2009 review adds that far-infrared saunas are sold to the public and that manufacturers claim numerous health benefits. The sources reviewed do not date the first consumer infrared sauna.

A separate lineage from the Finnish sauna

A 2024 review by Laukkanen and Kunutsor describes Finnish saunas as operating at roughly 80 to 100°C with dry air of 10 to 20 percent relative humidity, and lists infrared saunas and Waon therapy as separate types of passive heat therapy. The sources reviewed do not establish a historical link between the Finnish tradition and Japanese or commercial infrared forms.

Infrared, far-infrared and Waon

Infrared sauna and far-infrared sauna are used for heated cabins in which the heat source is described as radiant, as opposed to a stove heating the air. Far infrared is defined in one review as 3 to 100 micrometers, with a sub-band of 3 to 12 micrometers discussed for biological effects. Waon therapy is a specific protocol, usually a 60°C far-infrared dry sauna followed by rest under a blanket, so it is narrower than the commercial term.

Dry sauna, thermal therapy and heat therapy

Research papers use several umbrella labels. A 2018 systematic review studied regular dry sauna bathing across 40 clinical studies, and a 2025 review used passive heat therapy to group Waon therapy, balneotherapy, Finnish sauna and other methods. A 2026 review used heat therapy for saunas, hot spring bathing, hot water immersion and mudpack therapy. Because these labels cover different temperatures and exposures, a finding for one cannot be assumed to apply to an infrared cabin.

Protocols used in studies

In most of the studies reviewed, Waon therapy was a supervised program. Patients spent 15 minutes in a far-infrared dry sauna at 60°C and then rested for 30 minutes in bed covered with a blanket. In a multicenter trial this was done once daily for 10 days in hospitalized patients, and in a pilot study of chronic fatigue syndrome it was done five days a week for four weeks. A meta-analysis of heart failure trials described the same pattern, five times a week for two to four weeks.

Commercial and experimental sessions

Experimental sessions outside Waon vary. A 2026 laboratory study used a single 45-minute far-infrared exposure at 65°C, and a firefighter study used a 15-minute exposure after emergency calls. A trial in athletes used about 43°C after resistance exercise. The sources reviewed do not describe typical session lengths or temperatures in commercial settings, so they are not described here.

What participants may experience

In the 65°C laboratory study of 12 healthy adults, rectal temperature rose by 1.4°C, heart rate rose from 74 to 153 beats per minute, sweat rate averaged 1.4 liters per hour, and participants rated the heat as extremely hot and extremely uncomfortable. Blood pressure fell after exposure. Exposure at lower temperatures, such as the 60°C used in Waon, was not measured in that study.

Clinical research targets

Waon therapy and far-infrared sauna have been studied mainly in chronic heart failure and in people with coronary risk factors such as hypertension, diabetes and smoking. Authors of a 2010 review also reported use in severe peripheral arterial disease, and a pilot study examined chronic fatigue syndrome. A 2009 review lists chronic pain, chronic fatigue syndrome, obesity and cholesterol reduction among the claims it assessed.

Wellness and recovery claims

Manufacturers are reported to claim numerous health benefits for far-infrared saunas. Studied wellness uses include recovery after exercise, examined in a crossover trial of 16 male basketball players, and sweating as a route for removing environmental chemicals, examined in a small crossover trial. The sources reviewed do not document why consumers choose infrared saunas in everyday life.

Heart failure

A multicenter trial randomized 149 hospitalized patients with advanced heart failure to Waon therapy (76) or control (73). Waon therapy was given daily for 10 days. The authors reported improvements in symptom class, six-minute walk distance and cardiothoracic ratio only in the Waon group, but the change in the primary endpoint, plasma BNP, did not reach statistical significance. Several authors were affiliated with a Waon therapy research institute.

A 2018 systematic review searched for infrared and Finnish saunas in heart failure; only infrared studies met its criteria. Seven of nine studies were pooled. The protocol of 60°C for 15 minutes, five times a week for two to four weeks was associated with lower BNP and cardiothoracic ratio and higher ejection fraction, with no effect on blood pressure. Evidence strength varied from moderate to insufficient, and long-term effects were not established.

Blood pressure and vascular function

A 2009 review of nine papers found limited moderate evidence for normalizing blood pressure and for congestive heart failure, and consistent fair evidence against a cholesterol-lowering effect. An uncontrolled before-and-after study of 25 men with coronary risk factors reported improved flow-mediated dilation after two weeks. In 10 healthy women, a single infrared sauna session did not differ from rest or exercise on blood pressure, arterial stiffness or heart rate variability. A 2025 review of passive heat therapy found infrequent effects on resting blood pressure.

Pain, fatigue and recovery

The 2009 review rated evidence for chronic pain as fair, from a single study, and for chronic fatigue syndrome and obesity as weak, each from a single study. A 10-patient pilot of Waon therapy reduced perceived fatigue but not pain, with no control group. In 16 athletes, one post-exercise session was associated with less soreness and a smaller fall in jump performance. A PubMed search did not locate a systematic review by Kanji on infrared sauna and pain.

Finnish cohort findings do not transfer

A Finnish cohort of 2,315 men followed for a median of 20.7 years found lower rates of sudden cardiac death with 4 to 7 sauna sessions a week than with one (hazard ratio 0.37, 95% CI 0.18 to 0.75). That study concerns Finnish sauna bathing, which runs far hotter than Waon protocols, and it is observational. It offers no direct evidence about infrared saunas and should not be applied to them.

Sweat and detoxification claims

In a crossover trial of 10 women, pesticide metabolites were detected in sweat, and three urinary metabolites rose slightly after infrared sauna use. No definite sweat-to-urine correlation was shown. The authors framed this as raising questions about sweat and excretion. The study did not measure health outcomes, so it cannot support a claim that infrared saunas remove toxins.

Limits of the evidence base

Most infrared sauna and Waon studies are small, short, uncontrolled or conducted by the group that developed the method. A 2018 review of dry sauna bathing found only 13 randomized trials among 40 studies, most with fewer than 40 participants. A 2026 review found most heat therapy studies lacked control groups and were heterogeneous.

Heat strain and circulation

Far-infrared exposure at 65°C produced a rise in core temperature, an 11.6 percent contraction of plasma volume and a sweat rate of 1.4 liters per hour in healthy adults over 45 minutes. In firefighters, a 15-minute session after maximal exercise raised temperature and heart rate and lowered heart rate variability, which the authors said might interfere with recovery. These are physiological measurements and do not give rates of harm.

Reported adverse events

The multicenter Waon trial reported no serious adverse events, and the chronic fatigue pilot reported none. A 2026 review of heat therapy described serious acute events as rare but noted that few studies targeted adults aged 65 and over or reported comorbidities systematically. A 2018 review of dry sauna bathing found one small study of 10 men reporting reversible disruption of spermatogenesis and called for better adverse-event data.

Precautions and care boundaries

A 2026 review found that safety margins in frail older adults and in people taking beta-blockers are not well defined, and a few small studies suggested larger blood pressure falls in beta-blocker users. The 1995 study of thermal baths was carried out under catheter monitoring in patients with heart failure. The sources reviewed do not address infrared saunas in pregnancy, in children, or in people with implants, and they give no rates of dehydration or heat illness. Heat exposure should not replace or delay assessment or treatment of heart failure, chest pain, or other conditions.

Training and regulation

No professional register, training standard or protected title specific to infrared sauna or Waon therapy was found in the sources reviewed. Waon therapy in the studies was delivered in hospital and rehabilitation settings.