Data for the selected outcomes were extracted and entered into Review Manager Software (version 5.3). Data were expressed as a weighted mean difference (MD) and 95% CI. Fixed-effect (FE) model was used to pool the data. Whenever there was a heterogeneity, random-effect (RE) model was applied. Standard deviations (SD), if they were not reported, were calculated from means and 95% CI. The study results were combined depending on the method of prescribing montelukast (intermittent or continuous). In one trial, preschool and school-age children were included ; we used the preschool data only.