It was 31 degrees in Dallas on Monday, but that wasn’t cold enough for Brittany Justice. So the 22-year-old stripped down to her underwear, put on gloves and socks, and entered a cylinder where the temperature plunged to negative 211 degrees Fahrenheit.

In subjecting her near-naked body to temperatures colder than Antarctica (where, at the Amundson-Scott South Pole Station, it was a relatively balmy -5 degrees), Justice joined the shivering throng of Americans engaging in cryotherapy, the new treatment for everything from cancer to crow’s feet.

Cryotherapy uses sub-freezing temperatures to jolt the body into better health. Although its practice is said to have originated with Toshima Yamauchi, a Japanese doctor who in 1978 began using cold to treat rheumatoid arthritis, its history extends thousands of years. “The ancient Egyptians, and later Hippocrates, were aware of the analgesic and anti-inflammatory properties of cold,” a report on cryosurgery in the Journal of the Royal Society of Medicine said.

Doctors today use it to treat cancer — in particular, cancers of the prostate, cervix and lung — and it has recently been touted as a means to prevent hair loss in chemotherapy patients. The use of super-cold temperatures to treat arthritis and joint pain is a high-tech extension of old treatments like ice packs and ice baths. (Here, the University of Missouri recommends frozen bags of corn or peas for pain relief.)

And it is increasingly used by professional athletes — such as the Dallas Mavericks and New York Knicks pro basketball teams and the elite distance runners at Nike’s Oregon Project — to reduce inflammation and shorten recovery.

But in the past few years, cryotherapy has morphed from a medical treatment to a spa service, and people are now using it as a beauty treatment and to increase energy.

At Cold & Thirsty, a “juicery and cryosauna” in the suburbs of Los Angeles, patrons can enjoy organic, cold-pressed juices or almond milk before stepping into the chamber where liquid nitrogen drops the temperature to as low as 250 degrees below zero Fahrenheit. Clients can pay $70 for one session or buy a monthly membership for $400 that entitles them to freeze themselves once a day. (Unless prescribed by a doctor, cryotherapy is not covered by insurance in the U.S., although it is in some parts of Europe.)

Co-owner Katie Kaufmann said she joined with Brooke Rewa to open the business in 2015 after her own positive experiences with cryotherapy in Texas.

Two to three minutes in Cold & Thirsty’s cryosauna results in the reduction of the skin’s surface temperature by 30 to 50 degrees. The exposure is not long enough to cause frostbite or permanent injury, she said, just long enough for the skin to send messages to the brain that act as a stimulant to the regulatory functions of the body. Cryotherapy has “incredible anti-aging and anti-inflammatory properties, as well as benefits for weight loss, chronic joint disorders, chronic pain and decreasing injury recovery time by 50 percent,” Cold & Thirsty’s website says.

The Food and Drug Administration has yet to weigh in on those claims, athough it does regulate cryotherapy machines sold as medical devices, a spokeswoman said. Nor has it addressed the science behind the treatment: the body’s fight-or-flight response to a stimulus it perceives as life-threatening or potentially injurious — a perception that is sometimes accurate.

Basketball player Manny Harris was cut by the Cleveland Cavaliers in 2011 after he suffered a burn on his foot after wearing a wet sock during a cryotherapy session. And there has been at least one death related to cryotherapy: that of a 24-year-old found dead in a Las Vegas cryotherapy chamber in October.

An autopsy determined that Chelsea Patricia Ake-Salvacion, the manager of the spa, died of asphyxia caused by low oxygen levels. She was apparently alone at the time of her death.

That wouldn’t have happened at a facility like Cloud Cryotherapy in Pittsburgh, where owner Tom Rodgers said no one is allowed to use the cryosauna without a technician present, and all workers are CPR and AED certified. “In general, when correct procedures are followed, it is a very safe treatment that has been used for decades around the world,” Rodgers said.

Rodgers became interested in cryotherapy when working at a spa at a resort in California. “Every day, after I’d lock up, I’d do a heat/cold ritual using the steam room and cold plunge, which is just a cold-water immersion. Afterwards, I’d feel absolutely fantastic. It wasn’t because of any specific injury or pain I was alleviating at that time, but it was more of an overall sense of well-being and mood elevation.”

He began to research the science behind heat and cold therapies, and began to read about whole-body cryotherapy, which he tried after developing knee issues from running. Successful sessions at a cryotherapy center in New York led to him opening a center in his hometown of Pittsburgh. There, his clients have included professional athletes and dancers using the therapy for recovery from strenuous workouts, people suffering from auto-immune disorders and chronic inflammation, and people hoping to improve their general well-being and sleep.

Improved sleep is the primary reason that Justice, the 22-year-old Texan, gets cryotherapy three times a week at Mohler Cryotherapy in Dallas.

“It has really helped me with my sleep. I sleep like a baby,” she said. “I know a lot of people do it for energy, but some people get more relaxed."

What it's like

On his popular TV show, Dr. Mehmet Oz stripped down to his boxers and did a cryotherapy session in front of a studio audience. Afterwards, he said he was invigorated by the experience, but he appeared uncomfortable at times during the session and said he found it difficult to catch his breath.

The discomfort a person experiences usually varies based on what the person was expecting, said Cold & Thirsty's Kaufmann, who said any temporary shock is quickly dwarfed by the therapy's benefits. She credits cryotherapy with ending longstanding problems with digestion and inflammation. If she hadn't begun it, she said, "I would be on medication."

“The actual treatment itself is much more tolerable than people would anticipate after hearing about temperatures like -200 degrees,” Rodgers said. “Most of the cold will be felt in the legs as the body’s first response is to bring blood from the extremities to the core to preserve heat. Invariably, people are surprised at how quick the two or three minutes go by,” he said.

The typical chamber is a cylinder in which the person stands with his head exposed. At minimum, the user must wear gloves and socks since extremities are most vulnerable to freezing temperatures.

More study needed

There have been a handful of studies as to the efficacy of modern uses of the therapy, with most concluding that there are at least modest benefits, but more study is needed.

In a study of highly trained runners, the authors found a slight improvement in recovery and a general sense of well-being, but cautioned that “the lack of evidence on adverse events is important given that the exposure to extreme temperature presents a potential hazard.”

Those hazards are pronounced in people with certain conditions.

Experts caution that cryotherapy should not be attempted by pregnant women, those with hypertension or heart conditions, lung or bleeding disorders, Raynaud’s syndrome, kidney or urinary tract diseases, or a history of seizures. Some cryotherapy websites also suggest that a session can induce a cold sore in people prone to them.

For people who are interested in the benefits of cold-temperature therapies but not at temperatures 100 or more degrees below zero, there is evidence that even milder forms of cold exposure may have benefits. Researchers at the University of Michigan report that worms exposed to cold temperatures live longer, and the Scripps Research Institute found that the same holds true for mice.

Moreover, for people who live in cold climates, the easiest form of cryotherapy may be a swim. In Finland, researchers studied women who plunged into icy water for 20 seconds, similar to the Polar Swim events popular across the U.S. Blood analysis showed a spike in the levels of chemicals that help with pain suppression.

Other research in the U.S. showed improvement in the immune systems of athletes after cold-water immersion. And another study on whole-body cryotherapy concluded that, while it may assist with rehabilitation from injuries, athletes should “remain cognizant” that ice packs and cold-water immersion “offer comparable physiological and clinical effects” to commercially offered cryotherapy.

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