It's one of the most commonly used drugs for one of the most commonly suffered medical conditions in Britain today. So when it was revealed last week that, far from improving asthma, Ventolin could actually worsen the problem, a lot of people were understandably alarmed.

There are as many as 8 million diagnosed asthmatics in the UK, and the number currently being treated is around 5 million. Every week up to 18,000 people go to see their GP after a first attack of wheeziness - an astonishing 42% of the population has had one by their mid-30s. Among children, the condition is threatening to reach epidemic proportions: one in eight now has asthma, up sixfold on a generation ago.

For the vast majority of sufferers, Ventolin will almost certainly be part and parcel of their treatment, as ubiquitious to their care as an aspirin is to the chronic headache-sufferer. Ventolin - also known as salbutamol or salbuterol - is a short-acting drug which is usually delivered via an inhaler. It works by relaxing the airways, making it easier to breathe.

The problem, according to doctors at the American Academy of Allergy, Asthma and Immunology in San Francisco, is that a compound within salbutamol could weaken the anti-inflammatory effect of the steroids that are often taken along with with it. Patients who take the drugs frequently could find a build-up of the problem chemical within their bodies, which would mean that the steroids become less efficient.

So should the nation's asthma sufferers - and, with the numbers of youngsters affected particularly on the rise, their parents - be concerned? New studies are being commissioned to find out the extent of the problem, but the message from specialists and sufferers' groups in the UK is: this isn't something that should keep you awake at night.

Ventolin is a type of drug known as a "reliever". In other words, what it does is relieve the symptoms of asthma by opening up the tubes that have become constricted by an asthma attack. It is, in effect, the sticking-plaster of the asthma sufferer's world: when you feel asthmatic, you reach for your Ventolin just as, when you cut your hand, you reach for the Band-Aids.

Except, says Professor Martyn Partridge, professor of respiratory medicine and medical adviser at the National Asthma Campaign, you shouldn't see it as a cure-all. "It's far more important to realise that, if you take the low-dose inhaled steroid that has transformed life for millions of people, you wouldn't need the remedy of ventilation," he says. "If you're currently using Ventolin more than three times a week, then you should be on a low-dose inhaled steriod. You'd take that regularly and you'd find you didn't need the salbutamol."

The fact is that salbutamol is designed to be taken only occasionally and not, as many asthma sufferers take it, regularly. For those who take it without steroids, as the easy solution to the inconvenient problem of a wheezy chest, it poses no risk at all in the way described at the US conferences, for the simple reason that the counter-effect is against the steroids.

For those who have followed doctors' advice and are taking inhaled steroids, is there any risk that the occasional whiff of salbutamol could diminish their effects? Partridge is scathing. "We've been here before," he says. "Similar fears were raised about five years ago and what we found was that the effect was clinically unlikely to be of any significance."

The advice from the National Asthma Campaign is that no one should be so worried as to stop taking their medication: it's common to be prescribed a combination of medicines and there's no reason to think that they present any risk.

According to asthma specialist Dr Mark Britton, who chairs the British Lung Foundation, if research bears out the current findings on salbutamol, the long-term solution will probably be an attempt to refine the drug to make it purer and more effective by ironing out the presence of the chemical that causes the problem in conjunction with steroids.

That, in time, would lead to improved treatment for people with asthma. But he stresses that salbutamol has been an extremely effective drug for four decades, and that the current findings need to be confirmed before further steps are taken.

· The Asthma Helpline is on 0845 7010203. The National Asthma Campaign's website is at asthma.org.uk