It has long been suspected that the inflammatory substrate underlying attacks of wheeze in preschool children is different from the substrate underlying attacks of atopic asthma in school-age children, even though viral colds are a common trigger. There is now a substantial body of evidence from epidemiological and airway sampling studies to support this view. The first convincing evidence that wheeze in preschool children is a different ‘phenotype’ of asthma was provided by the Tucson (USA) birth cohort study,1 which found that wheeze for many preschool children is not associated with atopy and that it resolves by school age. A recent Dutch birth cohort study of 3963 children supports these data, since only 178 (14%) of 1230 children with parent-reported preschool wheeze had a diagnosis of asthma at 7–8 years of age.2 Furthermore, in the few preschool children who have undergone invasive airway sampling, the typical pattern of chronic eosinophilic airway inflammation that is characteristic of atopic asthma has not been found.3 4

To date, few large trials have specifically targeted preschool wheeze, and clinicians have used therapies of proven efficacy in older asthmatic children, including a short course of oral steroids.5 Two recent randomised double-blind placebo-controlled trials (RCTs) of oral steroids in preschool wheeze performed by my research group, provide some evidence to inform practice. In the first study, preschool children (1–5 years of age) presenting to a hospital accident and emergency department were randomised to receive either a short course of oral steroids (20 mg once a day for 5 days) or placebo to be started by the parents at the first sign of their next wheeze attack.6 …