Recurrent respiratory symptoms in children are extremely common. A proportion of those children who experience recurrent respiratory symptoms have asthma—reversible airways obstruction associated with bronchial hyperreactivity, allergic inflammation of the airways, and a response to treatment with bronchodilators and regular prophylactic inhaled anti-inflammatory agents. Since we cannot easily measure bronchial hyperresponsiveness or inflammation and clinical correlates are not specific, diagnosis often depends on response to treatment. But how big is the proportion with asthma, how does that proportion vary with age, and are we successful in applying the asthma label and giving the asthma treatments to the right group of children?

The prevalence of asthma has undoubtedly increased in industrialised countries over the last few decades. Increases in rates of physician diagnosis of asthma are partially accounted for by changes in diagnostic preference, but there is consistent survey evidence for the increasing prevalence of symptomatic wheezing. Parent reported prevalence of attacks of wheezing in Oslo children aged 6–16 increased from 3.7% to 6.8% between 1981 and 1994.1 Exercise induced bronchospasm is closely related to asthma, and the proportion of 12 year old children in Wales whose peak flow dropped by more than 25% after running doubled between 1973 and 1988.2

It was equally clear in the 1980s that childhood asthma was underdiagnosed and undertreated. Eleven out of 31 Tyneside schoolchildren experiencing more than 12 episodes of wheezing per year and three out of 56 with 4–12 episodes per year had been offered a diagnosis of asthma by their general practitioner.3 Since then, growing awareness of the existence of childhood asthma and of the effectiveness and relative safety of regular inhaled prophylactic agents has led to considerably higher rates of diagnosis and treatment. Has the pendulum swung too far the other way? Are we now making false diagnoses …