What are the Risks and Benefits of a Cold Plunge?

In recent years, cold-water immersion, or cold plunging—the practice of briefly submerging the body, or parts of the body, in cold to icy water—has gained traction among open water swimmers and ice bath enthusiasts. Health influencers and wellness gurus promote a cold plunge for its supposed benefits, ranging from reducing post-workout fatigue to boosting immunity and enhancing mental well-being, but what does science say?

For the uninitiated, plunging into icy water may seem extreme, but many claim that it enhances their health and mood. “Anecdotal evidence is not bad evidence, because people in general do feel good when they're doing it...but there's no scientific evidence to back it up,” said François Haman, a biologist at the University of Ottawa, who studies how humans respond to extreme challenges, including cold exposure. Many studies looking into the ability of cold-water immersion to improve mood are short-term experiments that rely on self-reported questionnaires.¹ There is some evidence that cold-water immersion can increase plasma concentrations of endorphins, dopamine, and serotonin, leading to a “post-swim high.”² But, the longevity of this response is unclear, as are the downstream biological effects of these changes.³ As Haman noted, a transient increase in these chemical messengers does not necessarily translate to a fix to underlying issues causing anxiety and depression. He added, “It's hard to differentiate what is basically the effect of cold and the effect of just the social interactions that you get with cold plunging. Often, we make no distinction between the two, and obviously there's a huge distinction between the two,” said Haman.

Proponents of post-exercise cold-water immersion for recovery claim it can help reduce exercise-induced inflammation and muscle soreness and improve performance. While there seems to be an effect on perceived muscle soreness when compared to passive recovery, there is a dearth of solid evidence to suggest that cold-water immersion has significant physiological benefits.⁴

Photo of François Haman speaking with people in swimsuits in front of a lake with snowy mountains in the background. — François Haman, a biologist at the University of Ottawa, provides cold training to military and emergency services personnel around the world.
François Haman

In general, investigating these claims is difficult given the lack of research on cold-water immersion and the fact that there is no standardization in the frequency, intensity, or duration of exposure that allows scientists to compare between studies, said Haman. As such, high-quality randomized control trials are needed to assess the short- and long-term effects of cold-water immersion.⁵ However, given the nature of the intervention, it is difficult to run double-blind randomized control experiments.

Beyond the hype, the evidence for these proposed benefits and others, such as reduced inflammation, improved immunity, or enhanced metabolism, remains weak.² Even if clear benefits were to emerge from continued research on cold plunges, Haman said that safety would still need to be a top consideration. “What people don't realize is the health benefits are maybe not what they think they are, and they always forget about the risks,” said Haman, who added, “Ice water can actually bring tremendous risks.”

According to Haman, humans are far better adapted to heat than cold. Since migrating out of more tropical climates in Africa, human adaptations to colder climates have been mostly behavioral, not biological. In fact, humans start losing heat to their surroundings as soon as the temperature in the environment drops below skin temperature. This loss is even greater in cold water, where the body exchanges heat around 25 times faster than in cold air.⁶ Haman added, “In cold water humans are extremely vulnerable, and chances of surviving are measured in minutes if it's ice water.”

The body’s response to cold-water immersion is swift and often severe.⁷ A cold-shock response—which includes gasping and uncontrollable hyperventilation—can be dangerous, especially if it occurs underwater, increasing the risk of aspiration and drowning. “The risks of drowning are extremely high,” said Haman. A sudden drop in blood pressure can also occur as blood shifts from the extremities to the core, and the shock can also put strain on the heart, triggering fatal arrhythmias, even in otherwise healthy individuals. If cold exposure continues, hypothermia can set in. While frostbite may occur, this is a rare occurrence. Of greater concern are non-freezing cold injuries, which are a type of tissue damage that arise following sustained exposure to low temperatures that are just above freezing.⁸ These injuries, which can arise even after short immersions in cold water, can lead to permanent cold sensitivity and pain.

“It's never one size fits all,” said Haman, who added that responses to cold water can vary between people.⁹ Also, responses are not linear, and people can respond differently depending on a variety of factors including stress, hydration, and current health. This is why Haman, who has trained first responders and military personnel on cold exposure safety, said, “I see cold plunging or cold as more of a teaching tool than something that is the magic bullet to solve every single problem on the planet.”

Because of these risks, Haman said that it is important that individuals participating in cold water plunges consult a medical professional prior to beginning, have a buddy system and safety plan in place, gradually work up to colder temperatures, monitor body responses, and limit their exposures.