In April 2025, a cryotherapy session at a sports center in Paris turned fatal.
A woman in her late 20s died after a suspected nitrogen leak from a cryotherapy chamber. A client in her 30s was hospitalized in critical condition. Three people who tried to help also required medical treatment, and approximately 150 people were evacuated from the building. French authorities opened an investigation into the death.
It was not the first fatal cryotherapy incident to raise serious safety questions.
Ten years earlier, in 2015, a 24-year-old employee at a Las Vegas cryotherapy center died after entering a cryotherapy chamber alone after business hours. Her death prompted Nevada officials to launch a broader review of cryotherapy safety practices and standards.
These were people entering environments built around a technology marketed for recovery.
Yet the danger they encountered had nothing to do with sore muscles, fatigue, or the condition they hoped to address.
It came from the recovery environment itself.
And death is the most extreme outcome.
Whole-body cryotherapy has also been associated with frostbite, cold burns, frozen limbs, skin injury, and other adverse events. The American Academy of Dermatology cites one Finnish study in which 16% of participants experienced mild frostbite during whole-body cryotherapy exposure.
Meanwhile, standard whole-body cryotherapy protocols can expose a person to temperatures below −100°C for approximately two to four minutes.
That creates a contradiction that deserves far more attention:
Why should recovery require another extreme stressor that the body then has to recover from?
Someone may enter a cryotherapy center because their body is already under stress.
They may be sore after exercise, fatigued, or trying to reduce discomfort and get back to normal faster.
But cryotherapy deliberately adds another challenge: an environment so cold that the body immediately has to defend itself against it.
Blood vessels constrict. Cold receptors fire. Autonomic responses change.
The cardiovascular system responds, and the body begins protecting its core temperature.
That physiological stress is not an accident.
It is how cryotherapy creates its stimulus.
Cold exposure can produce useful biological responses, and properly operated cryotherapy is not inherently unsafe.
But there is an important difference between saying that controlled stress can be useful and assuming that the more extreme a recovery treatment feels, the better the recovery must be.
Those are not the same thing.
And that is where photobiomodulation takes a fundamentally different approach.
PBM does not need to push the body below −100°C. It does not require liquid nitrogen and does not need to create a freezing environment or force the body into an acute cold-defense response.
Instead, PBM uses controlled wavelengths of red and near-infrared light as the physical input.
Cryotherapy creates an extreme stressor to trigger a response. PBM delivers a controlled signal without requiring that same extreme stress.
For a technology designed around recovery, that difference is worth examining.
The Cryotherapy Safety Problem Is Bigger Than One or Two Accidents
The Paris and Las Vegas deaths are dramatic because they ended in tragedy.
But the more useful question is what the broader safety data show.
A 2023 international review of true whole-body cryotherapy identified 16 documented adverse events across five case reports and two randomized controlled trials.
The authors ultimately concluded that properly conducted whole-body cryotherapy can remain within acceptable safety limits when operators follow contraindications, screening protocols, exposure guidelines, and other safety procedures.
That context matters.
Serious complications do not appear to be routine, but this conclusion should not be misunderstood.
Cryotherapy requires strict safety procedures because the treatment stimulus itself is extreme.
Temperature and exposure time has to be controlled. Patients need to be screened. Moisture needs to be managed. Protective clothing matters. And nitrogen-based systems introduce environmental considerations that refrigerated-air systems do not.
The margin between a controlled stimulus and an unwanted injury cannot simply be ignored.
When the Treatment Stimulus Can Also Injure the Tissue
Frostbite is one of the clearest examples.
The same extreme cold being used to trigger a physiological response is also capable of damaging exposed tissue.
The American Academy of Dermatology has documented reports involving frostbite, frozen limbs, rashes, cold panniculitis, and severe cold burns following whole-body cryotherapy.
In one study from Finland cited by the organization, 16% of participants developed mild frostbite.
This does not mean 16% of every modern cryotherapy user will suffer frostbite, but it demonstrates a central problem:
The therapeutic stimulus and the injury mechanism can come from the same source.
At the right dose, extreme cold creates a physiological challenge.
Too much exposure, poor protection, moisture, inappropriate equipment, or other errors can turn that same challenge into tissue injury.
That is a very different safety problem from simply asking whether a treatment “works.”
And Nitrogen Changes the Risk Again
There is another distinction often lost in discussions about cryotherapy.
Not all cryotherapy systems are the same.
True whole-body cryotherapy generally uses refrigerated breathable air and includes the head inside the chamber.
Many partial-body cryosaunas instead use vaporized liquid nitrogen to create extreme cold while the user’s head remains above the unit.
The 2023 international safety review specifically warned against treating these technologies as though they were identical.
That distinction is especially important when discussing fatal incidents.
In the 2025 Paris case, investigators initially suspected a nitrogen leak from the cryotherapy installation. One employee died, one client was critically injured, three additional people required treatment after attempting to help, and around 150 people were evacuated.
Nitrogen is colorless and odorless. The problem is not that nitrogen is a conventional poison. The danger arises when it displaces enough oxygen from the environment.
A person can therefore enter a hazardous low-oxygen environment without the obvious smell, smoke, or visual warning that people normally associate with danger.
That is not a theoretical consideration when a fatal accident has already demonstrated what can happen when environmental control fails.
Now Ask the Question That Matters: How Strong Is the Recovery Evidence?
This is where the contrast becomes even more important.
Cryotherapy feels powerful.
Temperatures below −100°C are objectively extreme.
But the intensity of a physical experience does not tell us how strong the clinical evidence is.
A Cochrane review of whole-body cryotherapy for exercise-related muscle soreness found only four randomized studies involving 64 participants.
The evidence for the measured outcomes was rated very low quality, and the researchers concluded that there was insufficient evidence to determine whether whole-body cryotherapy meaningfully reduced muscle soreness or improved subjective recovery compared with passive rest or no cryotherapy.
Research has continued since then, and newer studies have reported possible benefits in selected populations and outcomes.
So the point is not:
“Cryotherapy does nothing.”
The point is:
A treatment can be extremely intense while the evidence for the outcome you want remains uncertain.
Recovery Already Has a Job to Do
After intense exercise, the body is already managing muscle damage, altered energy demand, inflammatory signaling, autonomic changes, and tissue repair.
That is the recovery process.
Now introduce extreme cold.
The body suddenly has another immediate problem to solve:
maintain its internal temperature while responding to a severe environmental change.
Is another major stressor necessary for the recovery goal we are trying to achieve?
Because there is a meaningful difference between a controlled challenge that has a clear purpose and simply assuming:
more extreme = more effective.
A recovery method should not create a new stressor that the body then has to recover from unless there is a clear reason for doing so.
PBM Starts From a Different Principle
Photobiomodulation, or PBM, also uses a physical stimulus.
But instead of extreme temperature, it uses light.
Specific wavelengths of red and near-infrared light are delivered under controlled parameters, and researchers study how those signals interact with biological tissue.
PBM research has examined mechanisms involving mitochondrial activity, nitric oxide, cellular signaling, inflammatory pathways, tissue repair, muscle function, and other physiological responses.
The controllable variables are very different:
wavelength, irradiance, dose, treatment time, treatment area, distance, pulse characteristics
There is no need to create a −100°C environment first. No tissue has to approach freezing. No liquid nitrogen is required. And nitrogen-related oxygen displacement is not part of the PBM mechanism.
Cryotherapy controls an extreme stressor. PBM controls a biological signal.
References
- Legrand FD, et al. Evaluating safety risks of whole-body cryotherapy/cryostimulation (WBC): a scoping review from an international consortium.
European Journal of Medical Research. 2023.
See article. - Costello JT, et al. Whole-body cryotherapy for preventing and treating muscle soreness after exercise in adults.
Cochrane Database of Systematic Reviews. 2015.
See article. - American Academy of Dermatology. Whole body cryotherapy can be hazardous to your skin.
See article. - Nevada Department of Business and Industry, Division of Industrial Relations. Division of Industrial Relations to Open Inquiry Following Death of Cryotherapy Center Employee. 2015.
See article. - CBS News. Woman dies after suspected nitrogen leak at Paris cryotherapy facility. 2025.
See article. - Maghfour J, et al. Evidence-based consensus on the clinical application of photobiomodulation.
Journal of the American Academy of Dermatology. 2025.
See article. - Son Y, et al. Effects of photobiomodulation on multiple health outcomes: an umbrella review of randomized clinical trials.
Systematic Reviews. 2025.
See article. - de Freitas LF, Hamblin MR. Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy.
IEEE Journal of Selected Topics in Quantum Electronics. 2016.
See article.
