From Turkish baths to Mexican sweat lodges, sweating for leisure and health certainly isn’t new. But lately saunas have spread from Finland’s forests and millionaires’ mansions to shopping strips around Australia.

Dozens of businesses – including multi-branch brands like City Cave, which is “aiming to hit 100 spas this year”, and Recovery Lab, with seven branches across the eastern states – are selling Australians the chance to sweat it out in infrared saunas, touted as a high-tech update to the ancient wellbeing practice.

Beyond the pleasures of relaxing and unwinding, saunas in general are sought after for purported health benefits such as muscle recovery, pain relief, heart health, anti-aging and “detoxification”.

While a traditional sauna works by heating the air, infrared saunas raise the body temperature internally by penetrating the skin. This means you can work up a sweat without the surrounding air being quite as hot, which many people find more comfortable. Compared with traditional saunas, the infrared variety are also much cheaper: to buy (about a third of the cost), install (as they often do not require professional assembly) and run (around a third to half the cost).

There is lots of data supporting some of the benefits of sweating in a standard sauna. They’re certainly effective for relaxation, which has a host of positive health outcomes in and of itself. Other standard-sauna claims have varying levels of research support. Heart-health benefits of traditional sauna bathing, for instance, are largely attributed to improved blood flow.

There isn’t as much research on infrared saunas yet – although it is plausible they can produce similar effects, says Dr Brent Bauer from the Mayo Clinic in the US.

Some research, with very small sample sizes, has found comparable benefits to those of standard saunas, including for people with heart disease and chronic heart failure, recovery from strength training and relief of pain and stiffness in patients with rheumatoid arthritis.

Detoxification, or removal of toxic substances from the body via sweating, is more contentious. Bauer says there is very little supporting evidence that saunas in general can “get rid of toxins”.

“What we would like to see is a group of participants with their toxin levels measured at baseline and again after sauna,” he says. “If the levels went down significantly, that would bolster the claims. To my knowledge, however, there is still no large-scale study like that.”

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“Of course, lack of evidence doesn’t mean it can’t be true – we just can’t medically justify such claims until there is substantial data in favour of it.”

While things have been relatively slow on the research front, this hasn’t stopped many studios from selling saunas’ detoxifying capabilities, although the larger sauna chains like City Cave do not make such promises.

What they do promise is a profitable business. Much of the proliferation of infrared saunas, in Australia and abroad, has been as a result of franchising. International fitness and sauna studio Hotworx, which opened its first Australian branch in South Yarra in 2020, tells potential franchisees they will “maximise revenue per square foot”, while City Cave says its systems are “tried and tested to ensure profitability and an easy-to-manage business”.

“Gyms have struggled since Covid,” says Prof Lorelle Frazer, a franchising expert. Saunas offer product differentiation in the health and wellness industry. “The new businesses … have changed their focus to emotional and spiritual wellbeing, rather than purely physical fitness.”

Franchising is a popular business model in new and emerging industries, Frazer says. It can help franchisees become more organised, while the franchisers become more accessible to prospective investors, leading to quicker growth.

“The wellness industry has capitalised on consumers’ willingness to seek out new products and services which will … make them feel good about themselves,” Frazer says.

The cost of feeling good? Around $45 for a solo session, which can range from 30-50 minutes, depending on the provider.

For would-be sweaters, there’s little to lose, provided you can afford it. Bauer says he’s had many patients who have used both traditional and infrared saunas. “Some prefer one type over the other,” he says, “but most generally find the experience beneficial – whether simply as an aid to relaxation, helping sore muscles or just as a social activity.

“In general, if you are finding benefit from your sauna experience, and your care team hasn’t raised any concerns, enjoy!”