UK scientists say they have found a new cause behind much of the damage asthma causes.

Cells lining the airways are squeezed to destruction during an attack, their research shows.

And drugs to prevent this, rather than manage its aftermath, might break the cycle of harm, the Kings College London researchers told the Science journal.

The airways of people with asthma are sensitive to triggers such as pollen, pets and exercise.

They become inflamed or swollen, causing symptoms including coughing, wheezing and breathlessness.

Existing drugs or inhalers can reduce this inflammation and help keep the airways open.

But repeated attacks can cause permanent scarring and narrowing of the airways.

During an attack, the smooth muscle surrounding the airways starts to squeeze and tighten, known as bronchoconstriction.

The Kings College London team studied this process in detail, using mice and human lung-tissue samples.

Lead researcher Prof Jody Rosenblatt said bronchoconstriction damaged the airway lining, resulting in long-term inflammation, wound healing, and infections that cause more attacks.

Until now, this lining damage had been overlooked, she told BBC News.

"This epithelial lining is the body's first line of defence against things like infections and yet it is getting damaged during asthma attacks," Prof Rosenblatt said.

"There's this constant wounding going on - it's a vicious cycle.

"If we can block the damage, we are hoping that might stop attacks from happening at all."

'Desperately needed'

One possible preventive treatment the researchers are exploring is an element called gadolinium, which appears to help - at least in mice.

But much more work is needed to see if it might be safe and effective enough to try in people - and that will take years.

Asthma and Lung UK research and innovation director Dr Samantha Walker said: "This discovery opens important new doors to explore possible new treatment options desperately needed for people with asthma."

The charity says it's essential that people with asthma continue to use their prescribed medications correctly - many should be able to get on with their lives without symptoms getting in the way, and for those who are still having symptoms it is important that they talk to their healthcare professional.

"We know that there are many people for whom existing asthma treatments don't work as well, so it's vital we continue to fund research to find new treatments that better tackle the causes of asthma."

In the UK, more than five million people have asthma, about one in every 12 adults and one in every 11 children.

Most people with asthma have two inhalers:

• a preventer to use regularly, to reduce inflammation and prevent symptoms
• a reliever, to quickly open the airways

Those having an attack should not delay seeking help and call 999 if:

• their reliever is not helping
• the attack lasts four hours
• they are worried at any time