London: Asthma could be cured within five years after scientists discovered what causes the condition and how to switch it off.

In a breakthrough which could change the lives of Britain’s five million sufferers, researchers at Cardiff University and King’s College London identified which cells cause the airways to narrow when triggered by irritants like pollution.

Crucially, drugs already exist which can deactivate the cells. They are known as calcilytics and are used to treat people with osteoporosis.

“Our findings are incredibly exciting,” said Prof Daniela Riccardi, from Cardiff University School of Biosciences. “If we can prove that calcilytics are safe when administered directly to the lung in people, then in five years we could be in a position to treat patients and potentially stop asthma from happening in the first place.”

Scientists knew that asthma was caused by inflammation in the small tubes which carry air in and out of the lungs, but did not know what was triggering it. However experiments on mice and human airway tissue found that calcium sensing receptor cells — which detect changes in the environment — go into overdrive in asthmatics, triggering airway twitching, inflammation, and narrowing. But when calcilytic drugs are inhaled, it deactivates the cells and stops all symptoms.

Dr Samantha Walker, director of Research and Policy at Asthma UK, which helped fund the research, said: “This hugely exciting discovery enables us, for the first time, to tackle the underlying causes of asthma symptoms. “Five per cent of people with asthma don’t respond to current treatments so research breakthroughs could be life changing for hundreds of thousands of people. If this research proves successful we may be just a few years away from a new treatment for asthma, and we urgently need further investment to take it further through clinical trials.”

The scientist are hoping that clinical trials will begin soon. The discovery could also pave the way for new treatments for chronic obstructive pulmonary disease and chronic bronchitis, for which currently there exists no cure. It is predicted that by 2020 these diseases will be the third biggest killers worldwide. The research was published in the journal Science Translational Medicine.