The oldest known medical text is the Ayurveda, which is dated to 568 BC. It predates Hippocrates, the “father of medicine,” by at least a century. One of the central methods it prescribes for treating illness is sweating. No less than fourteen different means of promoting perspiration are described in the manuscript.

Finland is considered the birthplace of the sauna, and it remains a fixture of Finnish society. It is estimated that over 2 million saunas exist in Finland today, which has a population of only 5 million people. Other societies have embraced sweat baths as well. There are Russian banais, Turkish hammams, and Native American sweat lodges. It is believed that sweat rooms were initially used as a means of cleansing when the weather was too cold to permit bathing in a pond or stream. As suggested by the Ayurveda, facilities used to promote perspiration have traditionally been used in the treatment of illness as well.

A Finnish proverb states, "Sauna on köyhän apteekki," which translates into English as "The sauna is a poor man’s pharmacy." Writing in 1643 American colonist Roger Williams observed that the Indians, “use sweating for two ends: first to cleanse their skin; secondly to purge their bodies, which doubtless is a great means of preserving them, especially from the French disease which by sweating and some potions, they perfectly and speedily cure." It is not known for certain what the “French disease” was, but some believe that it was influenza.

George Catlin, who devoted much of his life to painting and documenting the life of Plains Indians, included in his description of the Mandan sweat lodge the statement, “it is used by the sick as a remedy for nearly all the diseases which are known amongst them. Fevers are very rare, and in fact almost unknown amongst these people: but in the few cases of fever which have been known, this treatment has been applied, and without the fatal consequences which we would naturally predict. This custom is similar amongst nearly all of these Missouri Indians and amongst the Pawnees, Omahas, and Punchas and other tribes."

Given its traditional use in treating illness it is not surprising that the sauna is once again being recognized as a valuable resource in the management of various health challenges. Research has shown that sauna use can provide significant benefits to individuals with high blood pressure, heart disease, lung disease, chronic pain, and other health challenges.

The earliest saunas used an open fire to generate heat and rocks to concentrate and radiate the heat. Water would be thrown on the rocks periodically to generate steam to more evenly heat the room. While purists suggest that the term “sauna” should apply only to traditional Finnish steam rooms the term is generally used today to indicate any facility that uses heat to stimulate perspiration.

Radiant heat saunas are still in use today, but infrared saunas are increasing in popularity, especially among homeowners. This is because infrared saunas do not require ventilation nor use steam to disperse heat. Infrared heated saunas generally induce perspiration at temperatures between 110 and 140 degrees Fahrenheit rather than the 160 to 220 degrees typical of radiant heat units. Because of the lower room temperature, many people feel more comfortable during infrared sauna sessions. The lower temperatures are also believed to be safer for use by individuals with heart disease.

Perhaps because of safety concerns, most of the studies looking at the effects of sauna use by people with high blood pressure or heart disease have been done using infrared units. In contrast, radiant heat saunas have been used in all of the published studies looking at the effectiveness of sauna treatments in removing toxic substances from the body. Therefore, while it is likely that the observed benefits can be obtained by using either type of sauna, this cannot be stated with certainty.

A review of Internet sites promoting the use of infrared saunas might lead one to believe that a home sauna is actually the elusive Fountain of Youth. Reported health benefits include improved circulation, increased metabolism, elimination of bacterial and fungal infections, smoothing of scars, reversal of plaque in arteries, elimination of pain, prevention of cancer, and weight loss. One site even claims that use of their sauna will eliminate cellulite because “fat will be pushed out of your pores.”

When I was young my father used to sarcastically suggest, “If you see it on TV you can believe it!” Those words often come to mind as I view sites on the Internet. If he were alive today I’m quite certain he would be telling me, “If you read it on the Internet, you can believe it!” in the same tongue-in-cheek manner.

One of the most widely circulated claims is that a person will burn calories while sitting in the sauna. I have seen statements that as few as 300 to as many 1000 calories are burned per 30 minute session. The calorie burning claims almost always state, “Medical studies have shown that a 160 pound individual will burn up to “x” calories in 30 minutes.” After an extensive search I was finally able to find the “studies” the sites are referring to. There are not studies, in fact there is not a single study showing that people burn calories while sitting in a sauna. The “studies” refer to a single letter to the editor of the Journal of the American Medical Association published in 1981 in which the writer referred to the amount of heat absorbed by sweat as it evaporated. Another letter to the editor appeared in JAMA a few months later rebutting the first and explaining that the heat that was causing the sweat to evaporate was the heat of the room, not calories within the body. Nevertheless, the belief that multiple medical studies have shown that sweating involves a large expenditure of calories is firmly entrenched in the sauna industry and it is unlikely that many will question it. For example, I discovered that 600 calories per 30 minute session is the most widely quoted number, not because it is backed up by an actual research study, but because that was the number quoted by Dr. Oz on a 2009 episode of Oprah.

Another claim is that infrared saunas are more effective in ridding the body of toxic metals and other substances than conventional thermal saunas. Typical statements are “Far-Infrared saunas offer 7 to 10 times greater detoxification than conventional saunas” and “The average person sweats out 20% toxins and 80% waters! Conventional Saunas only average 3% toxins and 97% water.” Some sites even provide a list of references to published studies. Unfortunately, the referenced studies had nothing to do with the composition of sweat. I was unable to find any study that looked at the detoxification effects of infrared sauna sessions let alone one that supported the detoxification claims given.

Claims that infrared saunas penetrate 1 ½ to 2 inches into the body are also unsupported. The actual depth of penetration varies depending upon the type of infrared radiation used. The infrared spectrum is divided into three classes: near, mid, and far. Near infrared penetrates the most deeply, but even this goes no deeper than 1 mm, which is less than four hundredths of an inch. Mid infrared penetrates a half millimeter or less, and far infrared does not penetrate below the very top layer of dead skin cells.

The health claims of sauna distributors are clearly suspect and must be taken with at least a tablespoon of salt. If one goes beyond the sales hype and looks at what is actually known about sauna use specific benefits do emerge.

The benefits of sauna use are believed to result from the body’s response to thermal stress (rising temperature). As the body temperature rises, the heart rate increases. In conventional high temperature saunas the resting heart rate can nearly double and the amount of blood being pumped can rise by as much as 70 percent. Because blood vessels near the skin open to promote perspiration to maintain a normal body temperature blood flow to the extremities increases. This is accomplished at the expense of the body’s internal organs, which receive less blood flow than usual. This has been shown to trigger angina (chest pain due to an inadequate amount of oxygen reaching the heart muscle) in the high temperatures of conventional, but not in infrared saunas.

The bottom blood pressure number typically falls during a sauna session, but the top number stays the same. The body’s metabolic rate and consumption of oxygen increase in a manner similar to that seen with moderate exercise.

Circulating levels of growth hormone, nitric oxide, and beta endorphins increase. Nitric oxide is a chemical that relaxes arteries and improves blood flow. Endorphins are natural pain relieving substances that can also improve one’s sense of well-being. Muscles relax and tendons become more flexible. Joint capsules become more elastic and the viscosity of joint fluid decreases.

These thermal stress responses are most likely to bring improvement in diseases of the heart and blood vessels and conditions characterized by chronic pain. This is, in fact, what studies have shown.

What follows are summaries of what is known about the benefits of sauna use in various conditions.

Hypertension (High Blood Pressure): Several studies have shown an antihypertensive effect of sauna use. Interestingly, a significant improvement in blood pressure has been found with as little as one session every two weeks for three months. In one study the average blood pressure dropped from 166/101 prior to regular sauna use to 143/92 following sauna use. This is comparable to that achieved with most blood pressure medications. In another study individuals who sat in a far infrared sauna for 15 minutes daily for 2 weeks had an average systolic (top number) blood pressure of 110 compared to 122 in non-sauna users.

Obesity: Persons with obesity and hypertension were divided into two groups. Both groups performed fifteen minutes of exercise three times weekly for eight weeks. One group followed their exercise sessions with thirty minutes in a far infrared sauna. The sauna group lost 1.8 times as much weight and 4.6 times as much body fat. Blood pressures of the sauna group dropped from an average of 142.8/89.4 to 121.3/79.5 compared to a drop from 140.2/90.2 to 133.7/84.6 in the exercise only group.

Congestive Heart Failure: While the number of people studied has been small, studies have shown that sauna use (typically fifteen minutes five days a week) improves the ability of the heart to pump blood effectively, increases the level of activity that can be performed, and reduces the number of hospital admissions. Seventeen out of twenty participants in one study reported an improvement.

Premature Heart Beats: Early beats, called PVCs, are common in people with heart disease. One study showed that sauna use (fifteen minutes followed by thirty minutes bed rest compared to a group receiving forty-five minutes of bedrest) reduced the number of PVCs from an average of 3,161 to 848 per twenty-four hours while the number of PVCs in the control group remained at 3,097 per twenty-four hours.

Lung Disease: Lung benefits are seen primarily with traditional hot steam saunas. Improvements in asthma and bronchitis have been noted, both in total lung volume and in the ability to freely move air in and out of the lungs. The same was found in a group of men with chronic obstructive pulmonary disease (emphysema). Having a steam sauna session twice weekly for six months reduced the incidence of colds by 50 percent during the last three months of the study.

Depression: In a study involving 28 people those who participated in twenty far infrared sauna sessions over a four week period reported greater improvements in energy, appetite, and ability to relax than those in the control group.

Chronic Pain: One group of patients hospitalized for management of chronic pain received far infrared sauna sessions while another did not. Both took part in counseling, rehabilitation, and exercise sessions. At the time of discharge those in the sauna group were handling their pain better and had lower anger scores than the control group. Two years later it was found that 77 percent of the sauna group had returned to work compared to only 50 percent of the controls.

A group of women with fibromyalgia reported an average pain reduction of 50 percent following a single far infrared sauna session. After a total of ten sessions the degree of pain relief reported ranged from 20 to 78 percent.

Individuals with rheumatoid arthritis and ankylosing spondylitis (an arthritic disease of the spine) reported feeling less fatigue, pain, and stiffness during their sauna sessions. After eight twice weekly sessions there was a mild improvement in their arthritic condition between sessions.

Diabetes: A group of diabetic patients received three twenty minute far infrared sessions weekly for three months. They reported improvement in their quality of life as measured by pre and post treatment questionnaires.

Detoxification: Traditional radiant heat saunas have been used in concert with diet, exercise, and nutritional supplementation in several treatment protocols. Heavy metals such as lead, mercury, cadmium, nickel, and antimony are released in sweat, but the concentration in perspiration is not as great as that found in the urine. There are currently no studies reporting the effectiveness of infrared saunas either alone or in concert with other detoxification modalities.

Sauna use, whether conventional or infrared, is generally safe. Individuals with a history of heart disease should use conventional saunas with caution because the high temperatures involved have been shown to cause ischemia (a decrease in the amount of oxygen reaching the heart muscle). A sauna should not be taken after consuming alcoholic beverages because the dehydrating effects of the alcohol could compromise the body’s ability to deal with fluid losses due to sweating. Those using tranquilizers or other medications known to cause sedation should not use a sauna because of the risk of falling asleep and remaining in the sauna for a longer period than is generally recognized as safe. Women should avoid saunas for at least the first three months of pregnancy since elevated body temperatures have been known to cause birth defects.

In the final analysis, the primary benefit of sauna use appears to be relaxation. Raising the body temperature in the evening can result in a more restful sleep. This is because a falling body temperature promotes the onset of sleep. Consistent use may bring improvements in blood pressure, mood, and chronic pain, but claims that sauna use will burn a significant number of calories, eliminate cellulite, and remove significant amounts of toxins from the body should not be taken seriously.

If you are considering purchasing a sauna it is advisable to try a few sessions before doing so. If you have a friend or relative who owns a sauna they may be willing to let you try out their unit. If not, it should be possible to use one at a local spa. If you find the experience relaxing and enjoyable proceed with the purchase, but do not buy a home sauna based upon the exaggerated health claims of manufacturers and distributors.