Millions of asthma sufferers may be receiving inadequate treatment, writes Jeremy Laurance.

Drugs to combat the condition have worked by controlling inflammation, which was thought to cause the progressive loss of lung function.

But scientists from the University of Southampton believe the airways can also be damaged by environmental triggers, leading to scarring of the airway wall. The study in the New England Journal of Medicine found in these cases, inhaling steroids to prevent inflammation may not be effective.