Inflammatory processes affecting nasal and bronchial mucosa are similar in nature. The purpose of this study was to examine whether children with perennial allergic rhinitis, without underlying asthma, have impaired pulmonary function. We also investigated whether nasal corticosteroids and loratidine would improve the pulmonary function tests of those children with impaired lung function. Fifty subjects with moderate/severe persistent allergic rhinitis due to exclusively dust mite sensitization and no past medical history suggestive of asthma were assessed. The control group consisted of 26 matched healthy subjects. Subjects with airway obstruction, as detected by forced expiratory volume/1 s (FEV1) or forced expiratory flow from 25/% to 75% (FEF(25-75)) values <80% of those predicted, were treated with loratidine, once a day for 10 days, and daily nasal budesonide for 3 months. We found that 11 of 50 patients (22%) with perennial allergic rhinitis had impaired pulmonary function (FEF(25-75) values <80%), compared to 1/26 (3.8%) of the control group (p < or = 0.05). Reversibility was observed in 9/11 (81.8%), mean 24.7% +/- 10.3%. Within 3 months of treatment, 7/10 had FEF(25-75) > 80% of their predicted values as well as significant improvements in their FEV1 (p = 0.04), and FEV1/FVC (p = 0.04). We conclude that a substantial proportion of children with perennial allergic rhinitis have diminished FEF (25-75) values and reversible airway obstruction. Nasal corticosteroids improve the pulmonary function tests of these children with impaired lung function.