Those who tested the device reported a huge improvement in their quality of life â€“ equivalent to that normally achieved only through expensive drugs â€“ and were less likely to be admitted to hospital.
The machine filters out theÂ irritants and allergens that trigger inflammation in the lungs, including dust mites and pet hairs.
Asthma specialists are now calling for the air purification device to be made available on the NHS.
They say the annual cost â€“ Â£4,000 â€“ would pay for itself, as sufferers would spend less time in hospital.
Professor John Warner, a consultant paediatrician at St Maryâ€™sÂ Hospital and professor of paediatrics at Imperial College London, led the study.
He said: â€˜This device makes aÂ significant difference to peopleâ€™s lives, with an effect as big asÂ very expensive treatments, and it helps prevent the triggers of the disease.â€™
The year-long trial involved 282 people with poorly controlled asthma aged from seven to 70 from six European countries, including 54 British children.
The Protexo machine is placed next to the suffererâ€™s bed, and has a large arm which delivers a flow of pure, filtered air around their head while they sleep.
It clears allergens and dust particles with a new technology used in operating theatres to create sterile environments.
Two-thirds of patients had the real machine and the remainder had a dummy machine.
They switched it on when they went to sleep and turned it off when they woke.
Findings from the trial, published in the journal Thorax, showed that the quality of life for those who used the real machine was 15 per cent better than those given the dummy, based on questionnaire scores.
The patients who used the device, made by Swedish firm Airsonett, experienced a dramatic fall in levels of inflammation.
It was particularly noticeableÂ for those with the most severe asthma.
Professor Warner said there were fewer hospital admissions among the group using Protexo.
The benefits began to show within three to four months.
Annabelle Abrahams, 14, from Westcliff-on-Sea, Essex, who has had asthma since she was four, took part in the trial.
She said: â€˜I slept badly because I couldnâ€™t breathe, doing PE or running around with my friends was difficult and I had asthma attacks if I laughed too much.
â€˜My schoolwork suffered because I was tired and off sick a lot.â€™
With the help of the machine, Annabelle now sleeps through the night without coughing.
â€˜Iâ€™ve seen a dramatic change and real improvement in my asthma,â€™
she said. â€˜I sleep better, haveÂ fewer chest infections and enjoy PE and sport.â€™
The machine, which is not yet available for private purchase, costs around Â£2,000 for six monthsâ€™ use.