Image: Yana Iskayeva / Getty Images Get the Popular Science daily newsletter💡 If you wake up hungry and achy every morning, one man might have all the answers you need: Dr. John Harvey Kellogg. At the 1893 World’s Fair in Chicago, Kellogg, who is famous for creating Kellogg’s Corn Flakes, introduced the so-called Incandescent Electric-Light Bath. That innovation, which used electric bulbs as light therapy to apply heat to the body, laid the groundwork for the modern infrared sauna. The purported benefits of an infrared sauna offer plenty of promise—from limbering up our limbs to detoxifying our bodies—and the market is surging these days with expanding options inside wellness clinics and for the home. But can infrared saunas relax muscles, reduce stress, and detoxify? Results may vary, depending on what you’re using them for, said Dr. Vivek Babaria, a board-certified interventional spine and sports medicine physician at DISC Sports & Spine Center, who has seen interest in saunas—both traditional and infrared—rise post-COVID. What is an infrared sauna, and how should it be used?  Infrared light is part of the electromagnetic spectrum that can’t be seen by the human eye, but can be sensed as heat, as NASA explains. Like a traditional sauna, infrared saunas create heat, but there are some key differences. Infrared saunas don’t get as warm, usually reaching no more than 140 degrees Fahrenheit compared to a traditional sauna, which can reach as much as 212 degrees. [Related: The best infrared saunas] Unlike traditional saunas, infrared versions also don’t use a wood-burning stove or electric or gas heater to warm the air. Instead, they rely on lamps that emit specific infrared wavelengths of light to warm the body, with the potential to penetrate deep into the skin. “What science is trying to do is study how deep that wave actually goes,” Dr. Babaria said.  Based on the research that exists, such as this 2013 study, and his own opinion, Babaria suspects the answer is about one to two inches at most.   Do infrared saunas actually work?  But why do we need infrared wavelengths penetrating deep into our skin? In the field of regenerative medicine and biohacking, experts are exploring how energy, including infrared light, can stimulate mitochondrial activity, a process that could support the body’s ability to heal and regenerate, Babaria said. Mitochondria, often referred to as the powerhouses of the cell, play an important role in how our cells function and replicate.  The science is still in the early stages, but there is growing interest in how infrared light might activate these cell components, Babaria said. Some believe that if infrared energy can penetrate up to two inches deep into the body, it might stimulate mitochondria, enhance cellular activity and promote faster recovery for our aching muscles and joints.  “We can’t directly correlate infrared rays into stimulating mitochondrial activity because the science is limited in the research papers,” Babaria said. “In theory, it makes sense. If the cells are less than two inches deep and you stimulate them, potentially the mitochondria are more active.”  What benefits do infrared saunas provide?  What we do know, however, is that heat offers therapeutic benefits for our bodies. A 2021 meta-analysis found that heat therapy can reduce blood pressure and improve the ability of blood vessels to expand and contract properly. Small studies, published in 2022 and 2015, have found that heat from infrared saunas can help sore muscles post-workout. And a 2009 study found that infrared saunas can improve short-term pain and stiffness for those with rheumatoid arthritis. Time spent inside a sauna could also potentially make us more limber. A 2019 study of older adults practicing yoga inside a sauna found they enjoyed improved flexibility. “If you can do 15 to 20 minutes in a hot sauna, where you can move your legs and even do some stretching exercises, it might help improve your range of motion,” Babaria said.  As far as the sauna’s alleged detoxification benefits, however, Babaria is a bit more skeptical. The lymphatic system and the liver are the body’s primary organs that are responsible for detoxification, he said. While sweating through the skin in the sauna might help the appearance of pores, true detoxification happens inside our bodies—not through our skin. Should you use an infrared sauna?  Saunas—infrared or otherwise—aren’t for everyone. People who have difficulty sensing temperature changes or how hot something is due to thyroid or heart issues, autoimmune conditions, or peripheral diabetic neuropathy should avoid them altogether. And be careful not to get dehydrated. Babaria recommends no more than 15 to 20 minutes a day inside an infrared sauna and pairing it with water or electrolyte drinks. But whether it’s looser joints or better blood flow, there are plenty of reasons to sit inside an infrared sauna, Babaria said — even if it’s just to relax in a warm, cozy space and reset our mental health. “If it could just put you in the right mind frame,” he said, “the rest of the body will follow suit.”   This story is part of Popular Science’s Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know? Ask us.