I am a sauna and steam room enthusiast, and I often recommend "sweat bathing" to cleanse the skin, soothe sore muscles, or simply relax. Sweating in dry or wet heat can also be beneficial to patients with arthritis, asthma, or respiratory infections, and it can help speed recovery from overindulgence in food or drink. Sweating rids the body of excess sodium and other unwanted substances, including drugs and toxins; in this way it can take some of the workload off the liver and kidneys. (I recommend regular visits to saunas or steam rooms to patients with liver or kidney disease.) To avoid overheating in a sauna, I recommend limiting your time to 20 minutes at a stretch. Be sure to drink plenty of water before, during and after saunas to restore fluids. If you have high blood pressure or heart disease be sure to check with your doctor; overheating in a sauna can stress the heart.
Hot tubs can be very relaxing, and because they promote sweating they can be healthful as well. My main concern with hot tubs has to do with sanitation and the chemicals used for cleaning them. Unless properly disinfected, hot tubs can harbor bacteria that can cause skin and other infections. High levels of chlorine or bromine used in hot tubs can irritate the skin, nose and respiratory system.
Hot tub folliculitis is a rash caused by a bacterial infection that is commonly experienced after soaking a poorly sanitized hot tub, and can occur even if the water looks clean. Stay clear of tubs if the water is murky or green or doesn’t smell right. For santizing hot tubs, I recommend copper products, such as the Cleanwater Blue system that I use at home. It is chlorine free and very simple to use.
I don’t advise pregnant women to soak in hot tubs because the heat can raise the mother’s core body temperature, which can affect blood circulation to the fetus. (I don’t have the same concerns about the dry heat in saunas, which I think are fine for healthy pregnant women.)
The main risk of sweat bathing is staying in too long and fainting from overheating, but other accidents do happen. According to an analysis of data on hot tub injuries collected by The National Electronic Injury Surveillance System in the 18 years between 1990 and 2007, more than 80,000 people were injured in hot tubs or whirlpool baths seriously enough to wind up in an emergency room; nearly half the injuries stemmed from slipping or falling. However, in 10 percent of all cases, the problem was heat overexposure. In addition, the Consumer Products Safety Commission reported in 2009 that more than 800 deaths associated with hot tubs occurred from 1990 to 2009, nearly 90 percent of them in children under age 3.
The researchers who analyzed the injury data for a study published in the December 2009 issue of the American Journal of PreventiveMedicine recommended that for safety’s sake, it is best to use the hot tub for only 10 to 15 minutes, at a temperature no higher than 104 degrees. (The Japanese like their baths much hotter and seem to do fine. I keep my Japanese-style, stainless steel hot tub at 108-110 degrees.)
Andrew Weil, M.D.