Can plunging into an agonisingly cold ice bath REALLY ease your pain?  Holby ... trends now

Sitting in an ice bath for three minutes a day, five days a week, is an unconventional treatment that the no-nonsense Holby City character, Dr Jac Naylor, is unlikely to have endorsed.

But actress Rosie Marcel, who played the heart surgeon in the popular BBC drama for 16 years, is a devotee of the freezing dips to tackle the pain caused by her rare autoimmune condition.

'I go numb when I'm in the ice bath - but you quickly get used to it,' says Rosie, 46, who lives in Hertfordshire with her husband, Ben, 41, who owns a gym, and their daughter, Beau, eight.

'When I get out of the ice bath my skin's bright red. But then the endorphins and dopamine kick in - and I feel incredible.'

Rosie takes ice baths to ease the symptoms of Behcet's disease, an agonising immune condition that causes painful red lumps all over the body.

Behcet's syndrome, as it's also known, is caused by an over-reaction of the immune system, thought to be due to a combination of genetic, immune and environmental factors. As well as swollen lumps, symptoms can include painful mouth and genital ulcers, stiff and painful joints, eye inflammation (resulting in red eyes and blurred vision) and hypersensitive skin.

Treatments include steroids, immunosuppressants and biologic drugs (made from human or animal proteins, which reduce inflammation), to ease symptoms.

In Rosie's case it causes outbreaks of 'painful hard, red lumps' all over her legs, 'ranging in size from a 5p piece to a tennis ball' as well as 'loads of mouth ulcers'.

First diagnosed with the condition in her 20s, she had been taking immuno- suppressants for nearly 20 years, but with side-effects such as an increased risk of infections (Rosie says she was constantly ill), she decided to try out ice baths after reading about the potential benefits on social media.

Traditionally used for centuries in Scandinavia and Russia for their 'healing' properties, ice baths have become a social media trend, popularised by Wim Hof, an endurance athlete who once held the Guinness world record for swimming under ice.

Hof argues that cold water and deep breathing can bring a host of benefits, including speeding up metabolism to boost weight loss.

Ice baths - literally bathtubs full of icy water ranging from 0c to 15c - are available in gyms and spas, but can also be bought for home use. Some people resort to filling wheelie bins with ice, according to social media sites.

But while ice-bathing may promote feelings of elation and wellbeing, can it really benefit your health? And what about the risks?

The scientific evidence for their benefits is far from conclusive.

Certainly, when it comes to muscle recovery, the case is stronger, and elite athletes such as runners and footballers have long used cold-water immersion therapy (including ice baths and cold-water swimming) after intense training sessions - it helps ease muscle inflammation.

A review of 17 trials (in which the water temperature was 15c or lower) by the prestigious Cochrane group concluded that the practice did reduce muscle soreness — but said more research was needed as to its safety.