Cold Plunging Is All Over TikTok—But Is It Safe?

Cold plunges—or the act of submerging oneself in ice-cold water—have gained traction on TikTok recently, with the hashtag #coldplunge garnering more than 350 million video views. But the potential benefits of cold water immersion remain unclear—and it could be dangerous if done incorrectly.

“Cold water immersion does activate the stress response, so you will feel alert and awake because it’s part of the fight or flight response and a side effect of cortisol and adrenaline being released,” Mike Tipton, PhD, MBE, a professor of human and applied physiology at the University of Portsmouth’s Extreme Environments Laboratory in the United Kingdom, told Health. “But it can be therapeutic or dangerous, depending on the circumstances.”

According to Tipton, who researches the effect extreme environments like cold water have on the body, almost all of the research concerning the benefits of cold water immersion is anecdotal, meaning people report their own benefits without the scrutiny of a controlled scientific study.

“We have lots of very good evidence saying this is a hazardous thing to do if you do not do it properly, but you can do it safely,” said Tipton. “Whether you can get benefits from it is still the question.”

If you’ve been curious about cold plunging—and are considering trying it out on your own—here are some factors to consider first.

Good for Pain, Bad for Muscle Growth

Humans have been spending time in cold water for thousands of years, as part of religious ceremonies or to pray, and as means of exercise. In recent years, people like Wim Hof, a Dutch motivational speaker and extreme athlete, have championed cold water plunges and cold water swimming as a therapy for everything from depression to strengthening the immune system. 

The most well-researched benefit of cold water immersion is its effect on pain, according to Lee Hill, PhD, an exercise physiologist and postdoctoral fellow at the Research Institute for the McGill University Health Center in Montreal, who studies cold water swimming.

A meta-analysis of 32 controlled trials, published in 2021 in the journal Physical Therapy in Sport, found using heat or cold therapy within an hour of exercising both delayed the onset of muscle soreness. 

“We know that ice in a first-aid setting reduces inflammation and it at least helps to reduce the perception of pain,” Hill told Health. “Cold slows the pain neurons so they can’t transmit pain signals to the brain.”

But while research has shown that although cold immersion is good for pain reduction and inflammation, it also inhibits muscle regeneration, which means it can also delay recovery.

One 2015 study, published in The Journal of Physiology, found that immersing in cold water post-workout hindered muscle fiber growth, which led to both less strength building and muscle mass.

In a review published in 2021 in the European Journal of Applied Physiology, experts noted that most of the research on cryotherapy’s effect on metabolism, inflammation and tissue damage have mostly been conducted using animal studies, meaning the effect on humans is still poorly understood. If done routinely, the experts said that cryotherapy can interfere with the benefits exercise has on the muscles. But if done sparingly, it can be used to help a person recover if they need to get back to exercise quickly.

According to Hill, cryotherapy can be a promising part of treatment for conditions that cause pain. 

While post-workout cold therapy could have unintended consequences, it can be used to reduce pain and inflammation caused by conditions such as rheumatism and carpal tunnel syndrome, especially if the cold water is applied only to specific parts of the body, such as the hands. 

“It can be used as an adjunct therapy, not in place of, but as part of the treatment plan for pain,” Hill said, noting that cold water diverts blood flow to the area, reducing the amount of pain and tissue volume, or inflammation.

Cold Water's Effects on Mood

Most research looking at cold water’s effects on mood has focused on cold water swimming, rather than sitting in cold water during a cold water bath or standing in a cold shower.

A particularly popular case study, published in 2018 in the journal Lifestyle Medicine, detailed a 24-year-old woman in the U.K. who was on medication for depression and anxiety. After four months of cold water swimming, she reported being able to manage her mental health without taking medication.

That was just one person, but some of the same researchers published a 2020 study, also in Lifestyle Medicine, compared the mental health of 61 novice swimmers who took a 10-week course in outdoor swimming to 22 people who watched them from shore. The swimmers experienced greater improvements in mood and well-being than their shore-bound counterparts, however, the authors noted that they did not isolate why this was, and that exercise is known to improve mood.

In a 2017 review, published in the journal Experimental Physiology, Tipton and his colleagues note that preliminary studies have found that cold water immersion does stimulate the central nervous system and release hormones, including some associated with alertness and mood, but also appears to reduce the availability of the feel-good hormone, serotonin (at least in people who aren’t adapted to cold water immersion). 

It’s also very plausible that the exercise and social aspects of cold water swimming are what’s causing a shift in mental health rather than the cold water itself. 

“We need a study that looks at the social and psychological benefits of feeling like you’ve conquered the cold and gotten the social benefits of hanging out with people. I have yet to see these controlled studies,” said Tipton.

Hyperventilation, Blood Pressure Drops, and Drowning 

Both Hill and Tipton said they aren’t against cold water immersion, but they do worry that its booming popularity will lead to unsafe practices.

“Humans are tropical animals, so putting them in water that is 50°F or lower is a challenging experience,” Tipton told Health. “There are a lot of people providing cold water experiences now, these range from good to bad and everything in between.”

The body loses heat 25 times faster in water than in air. When submerged in cold water, the body diverts blood flow from extremities to the core organs—the heart, lungs, and brain—to keep those functioning so you can survive longer.

Blood vessels elsewhere in the body undergo peripheral vasoconstriction, which restricts the width of the blood vessels. When you emerge from the cold water into a warmer setting, your body reverses the process, something called peripheral vasodilation. The blood vessels dilate, pushing blood throughout the body. 

“Although it can have benefits for lymphatic drainage and circulation, it really isn’t without risk,” said Hill. 

When cooled blood moves from the extremities back to the heart, it can cause hypothermia even hours after rewarming. “If you’re taking medications to reduce blood pressure, cold water immersion can be dangerous because that secondary drop, when the cold blood goes back to the heart, reduces blood pressure,” Hill said. 

In a 2012 review, published in The Journal of Physiology, Tipton said that cold water immersion activates both the sympathetic and parasympathetic parts of the autonomic nervous system, which can cause cardiac arrhythmias, even in healthy people without a history of heart disease.

That initial shock of the cold can also present a dangerous situation.

“That shock can cause hyperventilation that can cause you to faint. If the person’s face drops below the water and they’re hyperventilating, you have a high risk for drowning,” said Hill, noting that drowning usually happens in the first minute.

Tipton added that drowning can happen with just a small amount of water. “The average amount of water someone inhales to drown is about half a breath-full,” he said.

Use the Buddy System and Start Slowly

Cold water immersion can be done safely, and Tipton said that if you do it in a safe way and are feeling benefits, there’s no reason you shouldn’t do it.

“There is good science of the direct relationship between cold water immersion and cardiac arrest. The evidence for the benefits is anecdotal, but that is still evidence. I’m not saying it isn’t beneficial, I’m saying it hasn’t been tested,” he said. “If you are doing it safely, and you find it has benefits, do it.”

According to Hill, you should always be cleared by your doctor before doing any type of cold immersion—even in your own bathtub. That’s the first step. If you’re cleared, the second is to never do it alone.

If it’s swimming, go with people who are experienced and who have the ability to rescue you in the event of a drowning. If you’re at home, let someone know what you’re doing and have them sit with or check on you.

He also advised to keep the 1-10-1 rule in mind. 

“The first minute is the most dangerous, that’s when you hyperventilate, your concentration begins to slow down, and you aren’t able to focus as well. During that first minute, it’s really important to keep your airway above the water,” he said. “Then you should have 10 minutes of very good movement before you become incapacitated and lose the ability to perform meaningful movement. That’s when it becomes a bit more dangerous.”

Finally, to practice cold water immersion safely, ease into it.

“If you are trying it for the first time, take your time and acclimatize, slowly reduce the temperature over days or weeks,” said Hill. “Don’t shock your body into doing it full on for the first time.”