A 2018 meta-analysis of nine clinical trials found that five weekly sessions of infrared sauna for 2 to 4 weeks, was associated with a significant reduction in brain natriuretic peptide (BNP — a marker of heart failure progression) and cardiothoracic ratio (an indicator of heart enlargement), and improved left‐ventricular ejection fraction, but no significant effect on left‐ventricular end‐diastolic diameter, left atrial diameter, systolic blood pressure, or diastolic blood pressure.
Waon (Japanese: “soothing warmth”) therapy is a form of IR sauna developed in Japan, used for patients with chronic heart failure and other conditions. Waon therapy has been reported to improve many indicators of heart function, including cardiac output, stroke volume, ejection fraction, while also having benefits in vascular function including decreased vascular resistance and blood pressure. In a 5-year open-label trial, patients receiving Waon therapy in addition to usual care experienced a decrease in cardiac death and rehospitalisation after cardiac events compared to patients receiving usual care alone.
Some infrared therapy proponents claim that the IR is an effective method for considerably raising the rate of energy expenditure in the body. Proponents typically quote the Journal of the American Medical Association stating: “A moderately conditioned person can easily sweat off 500 grams in an infrared room, consuming nearly 300 kcal, which is equivalent to running 2–3 miles. A heat-conditioned person can easily sweat off 600–800 kcal with no adverse effects. While the weight of the water loss can be regained by drinking water, the calories consumed will not be.” However, this conclusion drew significant criticism, at least because it implies that individuals living in warm climates, where liters of sweat are generated per day, would require hundreds or thousands of additional kilocalories to survive, which is known not to be the case.
There are claims of detoxification which lack scientific evidence.
The prevalence of serious health claims associated with infrared saunas has prompted some regulatory agencies to issue public safety warnings about the use of these devices. There were fears that patients may refuse conventional medical treatments in favour of infrared sauna therapy.