Cold water therapy: Does it work?

There’s no avoiding the growing popularity of cold water immersion; it's a hot topic. 

While some of us are (understandably) less keen, many swear by the rejuvenating effects of ice baths, wild swimming, and cold plunges.

But is there any evidence that submerging yourself in cold water can benefit your health?

Below, we examine the scientific evidence for some of the most common claims. We also provide some safety tips if you’re keen to try it. 

Cold water therapy: Old and new

Humans have feared and revered cold water for centuries. On one hand, they were acutely aware that cold water immersion can be fatal. But on the other, many believed it could benefit health.

In the 1700s, Scottish doctor William Buchan wrote a book called Domestic Medicine. In it, he warns of both the dangers and positive effects of cold water.

Buchan explains that people who live in busy cities and lead sedentary lives might benefit most. Cold salt water was even better, thanks to its “superior gravity” and “power of stimulating the skin.”

In recent years, ice swimming, cold baths and showers, and wild swimming in lakes, rivers, and the ocean have become mainstays on health influencers' social media feeds.

The scientific evidence of the benefits of cold water therapies is fairly sparse, though. Much of the research to date focuses on sports performance, so we’ll start there.

Precooling and sports performance

If you exercise in a hot environment, performance tends to drop as you heat up. So, some athletes “pre-cool” using cold water before starting.

According to a review, most existing studies on precooling are small, but the evidence suggests it may improve endurance and performance in hot environments. 

However, it’s important to note that if you aren’t exercising in high temperatures, precooling won’t help. And the type of exercise is important, too: Precooling might improve endurance in longer events, but will initially reduce performance in sprints.

Cold water for recovery after exercise

Some claim that cold water immersion after exercise speeds up recovery, reduces muscle stiffness and fatigue, and decreases muscle damage.

A meta-analysis of 20 studies concludes that cold water immersion significantly reduces muscle soreness and helps athletes recover more quickly.

And a Cochrane review — the gold standard for evidence-based healthcare — concluded that there was “some evidence” that cold water immersion delayed the onset of muscle soreness. 

However, they didn’t find evidence that it helped in any other way, and overall, they write that the “study quality in this review was low.” 

Cold water immersion and inflammation

Inflammation is an important immune response to injury or infection. But if it’s in the wrong place or continues too long, it can start to damage cells and tissues.

Scientists have found that inappropriate inflammation is linked to virtually every chronic disease. So, can cold water help reduce levels of unhealthy inflammation?

Although there has been little research into this, there’s some evidence that regular cold immersion might help reduce inflammation in the long run. 

One study compared experienced sea swimmers with inexperienced sea swimmers. The scientists found that the experienced swimmers released less inflammatory compounds directly after swimming, whereas the inexperienced swimmers tended to release more.

The authors suggest that the immune systems of regular sea swimmers might have adapted to the stress of a cold plunge, thereby reducing overall inflammation. 

How about the immune system more generally?

Some believe that cold water immersion might help bolster your immune system, helping it handle threats more efficiently. Some also suggest that people who enjoy wild swimming get sick less often, but there’s no strong evidence.

Despite its plausibility, there’s not enough evidence to support the theory yet. 

Some studies have spotted changes in the number and types of immune cells in blood after cold water immersion. But it’s not clear whether these make a difference to how susceptible someone is to illness.

What makes things challenging is the wide range of other factors that might influence the results.

And as we saw earlier, people who are experienced cold water swimmers likely respond differently to cold water immersion than inexperienced swimmers. 

Also, people who swim in cold water are often physically fit, which may also influence overall health and their immune response.

A review concludes:

“There is some evidence that the short stress of [cold water immersion] may prime the immune system to deal with a threat, and thus be beneficial.”

However, they also explain that this is just a theory at this point. 

The authors also mention another important open question: It’s not clear what “dose” is optimal — it might be that very frequent cold dips suppress the immune system.

Mental health and cold water immersion

One of the most commonly cited benefits of cold water immersion is improved mental health.

As with the other claims we’ve covered, there hasn’t been much research, and many factors muddy the waters.

For instance, being outdoors and exercising can boost mental health for some people, whether they get in the water or not.

Additionally, cold water swimmers often form groups and battle the cold together, building social bonds and a sense of community, both of which support mental health. 

With all these factors considered, it’s challenging to tease apart the role that the water’s temperature plays in elevated mood: Would a dip in the balmy Mediterranean Sea also boost mental health? 

Similarly, a case study from 2018 charts the progress of a 24-year-old woman who had experienced major depressive disorder and anxiety since she was 17. 

She started cold water swimming once per week, and her symptoms improved so much that 1 year later, she was medication-free.

A study investigating sea swimmers found they had higher self-reported well-being, higher energy levels, and less physical pain from health conditions.

On the other hand, some studies have found no differences in mental health between sea swimmers and non-sea swimmers. For now, the scientific evidence that cold water immersion benefits mental health isn’t compelling. 

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What does it all mean?

The TL;DR is this: There’s not enough evidence to prove that cold water immersion benefits long-term health, but it might help improve recovery after exercise. 

It’s also worth pointing out that although the evidence for mental health benefits isn’t watertight, the first-person stories you’ll find on social media are heartening. Some people really do seem to feel the benefit. 

However, if this is something you’d like to try, cold water immersion, and particularly wild swimming, is not without danger. So, if you’re considering a frigid dip, here’s some advice:

Staying safe during cold water immersion

Being submerged in cold water can be stressful for animals that evolved in warmer climates (like us). It can cause an irregular heart rate, hyperventilation, and, sadly, drowning.

Here are some tips to help keep you safe:

• Only swim in areas with lifeguards or other experienced swimmers or have a designated watcher.

• Agree on a hand signal to use if you need help, such as waving one hand.

• Wear a bright-colored hat, take a whistle, and use a tow float — write your name and an emergency contact on the float.

• Ease yourself into it: Start in the summer months and wear a wetsuit.

• Get into the water gradually rather than jumping or diving in. Allow your body to get used to the temperature before heading for deeper water.

• Don’t stay in the water for more than 10 minutes (even if you stop feeling cold).

• If you’re having difficulty, float on your back and use as little energy as you can to remain afloat.

• Once you’ve left the water, dry off and get dressed as quickly as possible. Make sure to pack a wind-proof outer layer.

• Your body may continue to cool for 30 minutes after you’ve left the water, so don’t drive during this time.

• Endocrine (hormone) conditions.

• Heart disease.

• High blood pressure.

• A family history of sudden or unexplained cardiac death.

• Vascular disorders, such as Raynaud’s phenomenon.

• Heart rhythm disorders.

• Lung disease, including asthma and recent lung infections.

• Seizure disorders, such as epilepsy.

This isn’t an exhaustive list, so if you have another health condition, check with your doctor before taking the plunge. And if you want a safer and warmer option, we have an article on the health benefits of saunas.