My first time lasted four seconds. Any longer and I would’ve started screeching, writhing around in agony, and probably calling out for my mother. I’m talking about cold plunging, of course, in a teeny tiny pool of water hovering somewhere around 7C. This was a few years ago when the trend was still in its infancy. The pool in question had been installed in my local gym and, out of curiosity, I’d decided to dip my toe in, a decision I regretted immediately and one that had me running straight into the sauna, where I proceeded to hyperventilate.

Imagine my surprise, then, to witness this form of psychological and physiological torture become a bona fide trend. Not just a whizzy wellness niche reserved for the particularly “woo”, like spirulina smoothies and spirituality haircuts (yes, really), but a mainstream obsession that some people are paying hundreds of pounds a month for.

Contrast therapy, as it’s called, has boomed in popularity in recent months, with many dubbing it 2025’s biggest wellness trend. Derived from Scandinavian cultures and taking its cue from the rich and the bio-hacked, contrast therapy is now common practice among gym-goers, Smart Watch users, and anyone who happens to own swimwear. Just last week, a friend and I were making plans to hang out when she suggested that we go for a “sauna and plunge” at her local gym, BLOK Clapton, which had recently opened a dedicated “hot and cold” therapy room fitted with a large sauna and four individual plunge pools of varying temperatures ranging from 10C to 4C.

No longer a newbie (there have been a few more cold-water plunges since that disastrous first attempt), I loved it. I didn’t quite make it down to the four-degree pool – unless you count the small part of my foot – but still, I left feeling refreshed and revived. The next day, I immediately booked myself back in for another session.

“With demand for contrast therapy growing massively over the past year, our decision to introduce HOT + COLD has been immediately validated, with over 5,000 visits in just the first month,” said Ed Stanbury, founder and CEO at BLOK. Similar services are popping up elsewhere, too. Like at the newly opened Rebase Recovery spa in Marylebone, a plush space inspired by wellness rituals around the world. At Rebase, in addition to individual contrast therapy sessions, members can also partake in “communal contrast classes”, though these are often combined with other treatments as part of wider recovery programmes.

“Unlike traditional contrast therapy, which typically alternates between hot and cold treatments to improve circulation and reduce muscle soreness, Rebase combines these treatments with the expertise of recovery specialists,” explains a spokesperson for the company. “Their team tailors each session to the individual’s needs, ensuring the therapy is as effective as possible for recovery, performance, and overall wellbeing.”

Elsewhere, in Canary Wharf, there’s ARC, which opened in January and has been dubbed the UK’s “first contrast therapy club”. The luxurious wellness space features a communal sauna that guests can use before dipping into the nearby ice baths. “We are incredibly lucky to have already become very busy,” say ARC founders Chris Miller and Alanna Ki. “What was once a niche recovery tool for athletes has now become an essential ritual for peak performance, stress resilience, and social wellbeing. ARC is bringing this to London in a way that’s never been done before.”

What makes ARC unique is its focus on community: members are encouraged to sauna and plunge together, possibly even finding people to “connect, vibe, and party with”. The idea is that, as society has shifted to become increasingly health-focused, the way we socialise is changing.

“Younger generations are drinking less than ever and seeking alternative ways to connect,” explain Miller and Ki. “Sauna and ice baths provide a natural dopamine high without the downside of a hangover.” It also taps into a wider trend of being “well” together rather than just individually. Consider the boom in running clubs and group exercise classes, for example. “With rising stress, burnout, and anxiety levels, people seek natural ways to regulate their nervous systems,” add Miller and Ki. “The hot-cold cycle helps balance stress responses, reduce cortisol, and improve mood. We’re seeing a surge in health autonomy and self-empowerment in overall quality of life. I also think people are investing more in meaningful experiences.”

As for the health benefits, well, that depends on who you ask. One study from January conducted by the University of South Australia found that cold-water immersion can improve sleep, lower stress, and boost overall quality of life. Those findings are reflected in sports medicine, where traditionally athletes will partake in some form of contrast therapy to increase blood flow and oxygenation in order to help their muscles recover faster. It’s scientifically proven to reduce limb pain as well as inflammation and soreness, and one study from 2021 found that routinely alternating cold water swims with sauna sessions could benefit our metabolic health.

Others claim the benefits stretch even further, with some studies suggesting contrast therapy can help skin and heart health, as well as support the immune system. Then there are the copious psychological benefits: studies found that cold water immersion may boost our mood, decrease stress, and slow the progression of neurodegenerative diseases.

But at approximately £28 a pop, the question is how often do you have to do it to feel the benefits? “It’s not just a quick fix,” says Danyl Bosomworth, founder and CEO of Brass Monkey, which produces ice baths. “Sure, one plunge can give you an instant boost like a reset button for your body and mind, but the real benefits come with consistency. Over time, it helps build resilience, regulate stress, and improve overall wellbeing. So, while it’s not a magic cure, it’s definitely more than just a temporary plaster.”

But just as contrast therapy is becoming more ubiquitous, so too are concerns about how it might actually be damaging our bodies, specifically our nervous systems. That’s the theory touted by Liz Tenuto, aka The Workout Witch, a somatic exercise expert who focuses on healing the effects of trauma and stress on the body. In a blog post on her website, Tenuto argues that the euphoria experienced by many after a cold plunge may be deceptive. “The body, in its survival-mode response, releases a surge of stress hormones, creating a physiological illusion of having narrowly escaped danger,” she writes. “This temporary relief masks the underlying issues and may contribute to a cycle of stress and relief that fails to address the root causes of chronic stress.”

Tenuto is one of several voices arguing that cold plunging might actually be making us more stressed in the long run. “Cold exposure is a stressor, and while small, controlled doses can build resilience, too much can backfire, especially if someone is already dealing with high stress, adrenal dysfunction, or an autoimmune condition,” explains VJ Hamilton, a registered nutritionist specialising in autoimmunity. “It temporarily raises cortisol, which isn’t necessarily bad, but if someone’s stress levels are already through the roof, adding another stressor might do more harm than good.” This is particularly relevant for people with thyroid issues, like hypothyroidism or Hashimoto’s, Hamilton explains, as cold exposure can reduce the conversion of the active thyroid hormone, potentially making symptoms worse.

There are also some instances when it could hinder our nervous system. “For most people, contrast therapy actually stimulates the vagus nerve, which helps regulate the nervous system and supports stress adaptation,” says Hamilton. “However, if someone already has nervous system dysregulation such as in post-viral fatigue, long Covid, or fibromyalgia, intense cold exposure might overwhelm their system and make things worse rather than better.”

In other words, solving your health problems is sadly not as simple as flipping between a freezing cold pool and a boiling hot sauna. And while most of us won’t have saunas in our homes, who’s to say we can’t get many of the benefits of cold-water immersion from the comfort of our own bathrooms? “The benefits of cold exposure last for up to six days, so even a cold shower once a week is a good place to start,” says Sarah Huntley, performance psychologist at Goodwood Health Club in West Sussex, which runs retreats inspired by Wim Hof aka The Iceman, the Dutch athlete famous for his ice-cold water challenges and the breathing techniques he uses to make them possible.

“Recent research suggests deliberate cold exposure for around 11 minutes per week is optimum,” adds Huntley. “That’s 11 minutes spread across the week, so you could do three or four cold exposure sessions per week each for two or three minutes, either in a shower, ice bath, sea, lake, river, or even a tub in the garden.”

As with all wellness trends, it’s worth approaching this one with a healthy degree of scepticism. While it might work wonders for some of us, for others it could have the opposite effect, and possibly at a costly expense – most of the London-based contrast therapy places I’ve visited have memberships costing upwards of £200 a month. So, if it’s something you’re interested in, maybe start with a cold shower and take things from there.