Walk through any trendy suburb and you might find a new “wellness” studio offering ice baths or “contrast therapy” (a sauna and ice bath combo). Scroll social media, and you’re likely to come across influencers preaching the cold plunge gospel with cult-like zeal. Ice baths have gone mainstream. Initially practised mainly among high-performance athletes, cold water immersion is now a booming business model: sold as recovery, discipline and therapy all in one.

But the benefits are questionable and, importantly, ice baths can have health risks – particularly for people who have limited experience using them.

Cold water immersion isn’t a new concept. The “frigidarium” – a room with a cold plunge pool or bath – was a feature in most Roman bathhouses. For decades, athletes have used cold water immersion, such as swims in cold water, for recovery. But in recent years, with the proliferation of commercial cold plunge centres, there’s been an explosion in people using ice baths recreationally. Many people are even setting up their own ice baths at home. Social media shows serene influencers meditating through the pain, claiming it boosts mental health, serotonin, testosterone, and their metabolism. But does the evidence stack up?

Ice baths can reduce muscle soreness after intense training. However, the effect is modest and short-lived. Some research shows cold water immersion can improve mood after a single exposure in young, healthy people, but other research doesn’t find these benefits. Most claims about mental health, testosterone and weight loss aren’t backed by strong evidence. Rather, they’re anecdotal and amplified by influencers.

Businesses offering ice baths don’t always actively supervise patrons or monitor a person’s time in the ice bath. They may leave their customers to self-regulate, assuming people will know to get out of the water before they pass their body’s limits. What are the risks?

Cold water immersion triggers a powerful physiological response. Gasping occurs and breathing becomes rapid and uncontrollable. Heart rate spikes. Blood pressure rises. Staying in the water for too long can lead to hypothermia, a condition where a person’s core body temperature drops dangerously low. Shivering may begin within minutes in cold water.

As far back as 1969, researchers found even experienced swimmers could struggle after just a few minutes in cold water. Recently one of us (Sam Cornell) had to provide first aid at an ice bath venue in Sydney. A young man collapsed after staying in an ice bath for ten minutes.