Cold plunges are all the rage right now. The hashtag #coldplunge on TikTok has over 1.1 billion views, and features thousands of videos of people shivering and gasping through a soak in frigid water.

The toe-numbing practice is endorsed by celebrities, athletes, influencers and everyone in between.

Many say cold plunge benefits include relieving muscle soreness, aiding with recovery after workouts, reducing inflammation and boosting immunity. Some report cold plunges also yield mental health benefits, like improving clarity and reducing depression or anxiety.

But what does the science say about the benefits of cold plunges? We spoke to experts about cold plunges about what people should know before jumping in.

What is a cold plunge?

A cold plunge involves fully submersing the body in cold water — whether that be a bathtub, tank, pool or a natural body of water, such as a lake or the ocean. It’s also called cold water immersion or cold water swimming. Ice baths are a type of cold plunge, typically on the lower end of the temperature spectrum.

Although cold plunges have surged in popularity recently, the practice has been around pretty much as long as people have been near water, Mike Tipton, a professor of human and applied physiology at the University of Portsmouth, tells TODAY.com.

“Going back to Hippocrates and even Thomas Jefferson, Darwin and Florence Nightingale were all doing cold water immersion,” says Tipton, who leads research on cold water swimming at the University of Portsmouth’s Extreme Environments Laboratory.

How to cold plunge

A cold plunge involves immersing yourself in cold water — either quickly in and out or for several minutes. During a cold plunge, the water is typically between 50 to 70 degrees Fahrenheit or about 10 to 20 degrees Celsius, Dr. Kristi Colbenson, a sports medicine and emergency physician at the Mayo Clinic, tells TODAY.com.

The length of a cold plunge can vary depending on the water temperature and comfort level. The colder the water, the shorter the submergence should be, the experts note. In general, cold plunges typically last between five and 10 minutes, Colbenson adds.

The water should be no colder than about 53 degrees Fahrenheit or 12 degrees Celsius, at which point the risk of damage to the skin and tissues or other adverse events increases. The ideal temperature for cold water swimming is a bit warmer, or between about 65 to 75 degrees.

How long to cold plunge

Quite literally a quick plunge in and out counts as a cold plunge, but how long does it take for a cold plunge to work? It takes three to five minutes for the cold to penetrate beyond the skin, Colbenson says, at which point it starts to have a neuromuscular effect.

She adds that cold plunges typically last between five to 10 minutes, and Tipton cautions that plunging for longer than 10 minutes can increase the chances of being physically harmed by the cold.

People have long-touted the benefits of cold water but also warned of the risks, says Tipton, and throughout history it has been deemed both a cure-all and a health hazard. So what do we know now about how cold water immersion affects the body?

Cold plunge benefits

From a physiological standpoint, the biggest benefit from cold water immersion seems to be improvement in recovery, the perception of pain and delayed muscle soreness, says Colbenson.

A systematic review published in the journal Sports Medicine in February 2022 suggested that cold water immersion was an effective recovery tool after high intensity exercises, specifically HIIT exercises, TODAY.com previously reported.

Cold plunges may also reduce inflammation in the body. Why?

When the body enters cold water, this causes the blood vessels to constrict, especially in the extremities, to conserve heat at the core of the body near the heart, the experts explain.

"It slows down and inhibits blood flow to the legs and the arms and pushes (the blood) more towards the central aspect of the body," says Colbenson. "In doing so, you decrease that natural inflammatory response that occurs after exercise."

However, the reduction of inflammation after cold water immersion is likely temporary, the experts note.

“When you look at the literature, it does help with recovery and inflammation, especially if you’re a competing or training athlete,” Colbenson adds.

A cold plunge can also induce a heightened state of stress and send us into "fight or flight" mode, Colbenson notes, and the body will release a surge of norepinephrine and cortisol, the stress hormone.

Also known as a cold shock response, the initial gasping, hyperventilating and increased heart rate after jumping into frigid water can be dangerous — but it may also be the basis of some of the physical benefits, says Tipton.

“The belief is that if you consistently expose yourself to stress in a meaningful and structured way, your body will actually respond by improving its ability to respond to everyday stress,” says Colbenson.

However, the evidence that cold water immersion improves the body's immune function, is lacking, the experts note.

"From an immunologic standpoint, or your ability to fight infection, I give caution to that. ... There hasn’t been a good study that says there is a decreased propensity of getting infection if you use cold water immersion," Colbenson adds.

The lack of robust scientific evidence seems to be a running theme. “Whilst we know a lot about the science of the hazards, we know much less about the science of the benefits,” says Tipton, adding that more studies like randomized controlled trials (the gold standard in research) are needed. “We have hypotheses but no definitive experimentation yet," he adds.

Can cold plunges boost mental health?

When it comes to the mental health benefits of cold plunges, these are even less studied or understood, the experts note. However, there are many anecdotal testimonies about the mind-boosting effects of cold water immersion and a few possible theories.

In the short-term, cold plunges can increase levels of dopamine and endorphins, says Colbenson, which can contribute to a feeling of euphoria and heightened mental clarity or focus right after.

"That's how our body responds to stimuli that threatens us — we are ready to be clear in our ability to react," Colbenson adds. However, the mental clarity after a cold plunge seems to be short-lasting, she adds, and there isn't literature showing this is sustained over time.

The anti-inflammatory effects of cold water may also play a role. “There may well be, according to some models, an inflammatory component in depression and we know that repeated cold immersions decreases (inflammation),” Tipton adds.

Similarly, the hypothesis that repeated cold water exposures can make the body better able to deal with other stressors may apply to mental health obstacles, says Tipton, who co-authored a case study on a 24-year-old woman whose depression was treated with cold water swimming.

The patient felt an immediate improvement in mood after each immersion, the authors note, and experienced a gradual and sustained reduction in symptoms over time. One year after starting routine cold water swimming, the patient was reportedly depression-free and off medication, says Tipton. "Something's going on," he adds, but exactly what that is remains unclear.

There are several other factors that may impact a persons mental state after cold water immersion or swimming, the experts note. "They're doing some exercise, they're getting a sensation of overcoming a challenge and a sense of achievement," says Tipton, adding that cold plunges can also be a social activity.

“Even if it’s a placebo effect, that’s still an effect,” he adds. “There’s lots of potential things that could be going on and we need more experiments to isolate the active ingredient, to see what’s making a difference,”

Cold plunge risks

There's a right way and many wrong ways to do a cold plunge, the experts note, and certain people should avoid it entirely.

"We've spent probably 40 years looking at the hazards associated with going in cold water — from drowning to sudden cardiac death," says Tipton.

The surge in the hormone norepinephrine from cold water increases the heart rate, blood pressure and breathing rate, says Colbenson. For young, healthy people, that may be tolerable, she adds, but for people with any history of heart disease or cardiac problems (such as arrhythmias), it can be deadly.

People with any cardiac history, vascular disease or conditions like high blood pressure should probably avoid cold plunges, Colbenson says — regardless, everyone should check with their doctor before trying cold water immersion to be safe, the experts note.

People should also avoid doing cold plunges or cold water swimming alone, Tipton warns. "We want to make sure that people do it safely, and that means doing it in a controlled environment with other people or supervised," says Tipton.

Some people may be tempted to take things up a notch or drop the temperature, but the experts caution against overdoing it. "Colder is not necessarily better, and that cold shock response is potentially dangerous if you're in an uncontrolled environment," says Tipton.

"We know that response maximizes between 10 and 15 degrees Celsius, so you don't need to be going into iced water," says Tipton. Plunging for longer (or beyond about 10 minutes) is not always beneficial either, he adds. "There's a greater chance you become physically incapacitated by the cold."

Practicing cold water immersion in a sensible and risk-minimizing way maximizes the chance of it being beneficial, says Tipton.