BACKGROUND In atopic subjects, dysfunctions of the upper and lower airways frequently coexist and allergic rhinitis seems to constitute a risk factor for the occurrence of asthma in predisposed individuals. OBJECTIVE To evaluate whether in atopic subjects nasal inflammation could reflect changes in respiratory functions, 11 allergic children, sensitized to house dust mites (HDM), with rhinoconjunctivitis and asthma and 10 nonatopic controls (ctrs) were studied. METHODS All subjects underwent nasal brushing to detect percentages of nasal eosinophils (Eos %) and intercellular adhesion molecule-1 (ICAM-1) expression by nasal epithelial cells. In the same day pulmonary function tests, i.e. forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced expiratory flows at 25-75% of the vital capacity (FEF25-75%) and methacholine (MCh) bronchial inhalation challenge were also evaluated. RESULTS Pulmonary function parameters were not significantly different in allergic children and in ctrs (P > 0.05), while a significant increase in bronchial reactivity to MCh, expressed as Pd20 MCh, was detected in the former population (P < 0.05). As compared with ctrs, allergic children showed elevated Eos % and ICAM-1 expression (P < 0.05). When nasal inflammation and pulmonary function parameters were compared, a significant correlation was found between nasal Eos % and bronchial reactivity to MCh (P = 0.002). CONCLUSIONS These data support the concept of significant links between upper and lower respiratory tract involvement in atopic children sensitized to HDM.