Killer cold: the risks and realities of cryotherapy

On Air’s website boasts a 4.8 out of 5 review score for its cryotherapy unit, but one of the only two visible reviews appears to have been written by a dissatisfied customer a month before the nitrogen leak, translated here: “Very amateur. Contrary to all the instructions posted in the room regarding the importance of protecting my extremities, I was given nothing. In all the other centres I went to, I always had gloves and slippers. I had to interrupt the session before the end because my toes were frozen, and my feet still hurt two hours after the session. Choose specialised centres.”

Until an inquiry into what took place reaches a conclusion, it’s unlikely On Air’s cryotherapy unit will reopen. Inside the gym a receptionist told me the manager was not available to talk. When I called the following day, I was told, after stating that I was a journalist, “We don’t do cryotherapy any more,” and the line went dead. But other On Air gyms continue to offer the service, and there is no shortage of choice elsewhere.

In Paris, where there is a pharmacy on every block and the line between beauty salons and medical clinics is not always easy to distinguish, cryotherapy has become the latest requirement for on-trend spas. In the UK, there are now 96 venues offering cryotherapy listed on the hair and beauty salon booking website Treatwell.

A few hundred metres from On Air is a salon called Cryobar. When I visited, the receptionist told me that in the immediate aftermath of the On Air incident there was a drop in custom, but business quickly recovered. There has been no transfer of gym users, however, because as the receptionist explained, they cater to different needs.

“Our clients are looking for body sculpture, not recovery,” she said. “They have localised cryotherapy to get thinner.” Cosmetic applications are fast outpacing the sporting ones.

Despite what happened in Paris, fatalities or serious injury are rare within cryotherapy chambers. Ten years ago, an employee of a “rejuvenation” company in Las Vegas froze to death in a cryotherapy machine having entered it after work, against protocol and without any staff oversight. But these events make the news because of their exceptionalism.

Cryotherapy dates back at least as far as the ancient Greeks, who believed in the healing powers of cold water – “cryo” means cold and “therapeia” means cure. The recent popularity of cryo chambers can be traced to their adoption by sports teams such as the Welsh rugby side, Leicester City (during their Premier League-winning run of 2016, when the team suffered very few injuries), and famous individual sportspeople like Cristiano Ronaldo.

The first commercial cryotherapy practice in the UK didn’t open until 2009. Alla Pashynska was so impressed by the cryotherapy treatment she received at a Polish spa the previous year that she returned to Staffordshire and set up her own clinic in Stoke-on-Trent.

Eight years later she moved to London and now runs Ice Health on Kensington High Street, at the heart of one of the capital’s wealthiest neighbourhoods. She believes accidents like the one in Paris are caused by inferior equipment. (No information has been released on the make or model of On Air’s cryotherapy chamber). She told me a salesman once tried to sell her a chamber that did not have an internal oxygen monitor, and that “the oxygen monitor has to be built into the machine to pick up a small leak”.

Pashynska is something of a cryotherapy evangelist. She talks passionately about what she claims are its many benefits: the improvement of blood circulation, the strengthening of immunity, many anti-inflammatory effects, as well as hastening the repair of muscle damage, stimulating weight loss and improving skin.

Many of these claims are repeated in various ways by other clinics and, when we met, Pashynska had plenty of anecdotes to support them. She also cited a scientific paper published in 2023 in Cryobiology, a research journal reporting on low temperature biology and medicine, that examines the positive effects of cryotherapy on the treatment of chronic fatigue syndrome, though the paper concludes that its findings “should be interpreted with caution”.

Dr Joe Costello, associate head of research and innovation at the school of sport, health and exercise science at the University of Portsmouth, was part of the team that conducted the largest overview – a Cochrane Review – of scientific studies on the benefits or otherwise of cryotherapy on treatment for muscle soreness. A Cochrane Review “is considered the gold standard of evidence-based practice,” he told me recently. “We concluded that there was insufficient evidence to support the use of full-body cryotherapy as a treatment for muscle soreness or recovery.”

It’s because of this report, published in 2015, that the FDA in America has continually refused to support its use. And yet muscle soreness and recovery were the issues that jump-started the cryotherapy craze, and led the marathon runner in Paris to the On Air gym.

Then I asked Costello about the treatment’s other alleged benefits. “There is really poor evidence to substantiate any of those claims,” he said. “The largest amount of research is in the sports recovery area and even that is very limited. All other claims are another layer down in terms of available high-quality randomised controlled trials.”

I asked Costello why so many sports teams swear by its benefits.

“No one really knows,” he said. “My understanding is that nobody wants to be seen to be left behind. And there’s some evidence for a placebo or a perceptual benefit, where people think it is improving them.”

Pashynska estimates that around 65% of her clients come for preventative health treatments. It’s a market that is particularly susceptible to fads, and in recent years extreme temperatures have been all the rage, from the heat of saunas to ice baths and the cold water immersion popularised by the Dutch motivational speaker Wim Hof.

Ice Health offers a popular treatment called “contrast therapy”, that takes the body from +80C to -196C in three minutes. When I asked Costello if those temperatures are tolerable for the human body, he said, “The hottest temperature recorded on Earth is 57C, and the coldest is -89C. The temperatures you’re talking about far exceed the natural extremes, and people are going in their swimming gear, so there are potentially a lot of risks.”

Costello went on, “We found five case reports and two randomised trials that talk about adverse affects of cryotherapy. So there is a history of side-effects, including amnesia, cerebral haemorrhage, abdominal aortic dissection, dizziness, headaches, shivering, all recorded across the literature.”

Pashynska maintains that the key element in the treatment she offers is dry air. “If there was a little bit of humidity it would cause burns,” she told me, “and you wouldn’t be able to manage it.”

In common with all cryotherapy clinics, Ice Health has a consent form that clients must sign, listing contra-indications, the most important of which, Pashynska said, are heart conditions, “because of the obviously massive blood flow”.

What about vascular problems? I asked.

“On the contrary, it should help,” she said. But Costello told me that “cardiac, respiratory and vascular conditions could place cryotherapy users at risk”.

Cryotherapy chambers come in different sizes. Some are walk-in and affect the whole body, like mini saunas in reverse. Others, like the one at Ice Health, are tall, slim machines that look a bit like a fridge with an open top, where the client’s head remains above the chamber, poking through a fabric lid.

Pashynska prefers liquid nitrogen chambers to electric, because they are capable of producing the lowest temperatures and there is less risk of humidity. Cold air, even extremely cold air, feels much less cold if there is no liquid present in the atmosphere. When we met in Kensington, she used a hand-held machine meant for precision application for, among other things, targeting injuries and inflammation. Pashynska sprayed vaporised nitrogen at -160C on my hands and neck. It was cold, but nothing like the feeling of plunging into cold water.

When clients step into chambers like the one at Ice Health, they are encouraged to keep moving, partly as exercise, partly to distract from the cold.

One of Pashynska’s regular clients, a retired chief executive, comes twice a week for his three-minute stint. He suffers from macular degeneration, a condition of the eyes that can lead to blindness. The treatment for it involves receiving an injection directly into the eyeballs. A few years ago he was undergoing this grim ordeal every four to six weeks. Once he began receiving twice-weekly cryotherapy, the gaps between the injections stretched until there was a whole year between them.

He attributes this improvement entirely to the cryotherapy. “There’s no doubt about that,” he told me confidently. “I mean, it was obvious.”

The Harley Street professor treating him was pleased by the results, he said, “but it’s very difficult for him to say anything publicly positive about cryo. He just gave me a nod, and said ‘Great. Keep it up!’”

The retired executive doesn’t exercise when he’s in the chamber. “I just tap my feet,” he said.

I asked if he felt invigorated after a session?

“No,” he said. “You just feel glad it’s over, because it is cold and you can’t wait for it to end.”

A friend told me she recently tried walk-in cryotherapy at a European spa, wearing a swimsuit, gloves, headband, Covid-style paper mask and a pair of Crocs provided by the spa. Initially she was surprised by the softness of the cold vapour, which seemed much more benign than she had been expecting. But towards the end of her two minutes, “I felt the cold coming for me, like it was getting under my skin. I don’t think I’ve ever felt cold in my bones like that before.”

The sensation was most intense in her lower arm. When she mentioned this to one of the spa staff, she was told that she must have “inflammation” in that area. “I just thought, that’s weird,” she recalled. “I’ve never had any symptoms of that.”

But she felt an endorphin rush afterwards, and was keen to return for double the length of time the next day – four minutes, the maximum provided by the spa. Again she experienced the same biting cold, but this time in her lower legs, too. Afterwards she says she felt “exhilarated. On top of the world.”

When I was at Ice Health, a middle-aged female client was keen to use the cryotherapy chamber for the purpose of weight-loss. This is one of the most profitable claims made by cryotherapy industry: that very cold temperatures serve to burn calories through a process called thermo-genesis. Dr Adnan Haq, lecturer in sport and exercise science at the University of South Wales, told me that the research into this claim is ongoing. While it may be possible to attain substantial calorie burn from multiple WBC treatments, he cautioned that “the evidence for this weight-loss potential is tentative at best, and in my opinion WBC should not be advertised as an effective long-term weight loss tool.”

Dr Costello and his team conducted a study comparing three different time exposures of one, two and three minutes at a temperature of -135C in a WBC. They concluded that two minutes was the optimal exposure time before any possible anti-inflammatory benefits would be outweighed by the potential risks. He believes it likely there are many other adverse events that have not been reported widely in the literature.

Death from a nitrogen leak is probably the least likely risk of all. But do we heed health advice when something makes us feel good? Immersion in cold water – what wellbeing providers call “cold water therapy” and which is unregulated – can be lethal. Yet tens of thousands of people swear by it and swim throughout the winter. The tragedy in Paris may give pause for thought, but a burgeoning number of cryotherapy enthusiasts are unlikely to come in from the cold just yet.

Photographs: Shaw + Shaw; AFP