Asthma could be cured within five years, bringing relief to Britain's five million sufferers.
Scientists from Cardiff University and Kings College London have identified which cells cause the airways to narrow when triggered by irritants like pollution.
Drugs - known as calcilytics, which are used to treat people with osteoporosis – could be used to prevent an attack ever happening and ending the need to constantly carry an inhaler.
Professor Daniela Riccardi, from Cardiff University School of Biosciences said: "Our findings are incredibly exciting. 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."
Asthma is a debilitating long-term condition which can cause coughing, wheezing, chest tightness and breathlessness.
It blights millions of children's lives, forcing them to stay indoors to avoid allergens, and to avoid exercise for fear of bringing on an attack.
Scientists knew that asthma was caused by inflammation in the small tubes which carry air 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 (CaSR ) 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, the research - published in Science Translational Medicine - found.
Dr Samantha Walker, Director of Research and Policy at Asthma UK, who 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.
"Asthma research is chronically underfunded; there have only been a handful of new treatments developed in the last 50 years so the importance of investment in research like this is absolutely essential."
The scientists are hoping that clinical trials will begin soon.
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