OBJECTIVE To investigate the relationships between the severity of childhood allergic rhinitis (AR) and the peripheral blood eosinophil count, serum eosinophil cationic protein (ECP), total IgE (tIgE), and allergen-specific IgE (sIgE) levels. METHODS A total of 138 children with AR aged 3 to 17 (9.96 ± 3.78, x() ± s) years old were enrolled in the study. All children had persistent AR sensitized to house dust mites with a clinical history of 3 months to 12 (4.21 ± 2.72) years. The disease severity was evaluated using 10 cm-visual analogue scale (VAS), and the serum levels of ECP, tIgE and sIgE were determined using an ImmunoCAP system. Statistical analysis was conducted with SPSS11.0 software. RESULTS Among 138 children with AR, the VAS scores for global severity of rhinitis and nasal obstruction symptom were 5.32 ± 2.16 and 4.78 ± 2.45, respectively. Blood eosinophil count was 0.39 [0.24; 0.63] (M[P(25); P(75)]) ×10(9)/ml. Serum levels of ECP and total IgE were 10.60 [3.26; 30.80] µg/L and (2.50 ± 0.53) log kU/L, respectively. Serum levels of allergen-sIgE against Dermatophagoides pteronyssinus and Dermatophagoides farinae were 58.20[24.75; > 100] kUA/L and 54.95 [24.55; > 100] kUA/L, respectively. The VAS scores of nasal obstruction symptom, but not global severity of rhinitis, were positively related to the duration of AR (r = 0.215, P = 0.011) and the levels of serum ECP (r = 0.196, P = 0.022) in bivariate correlation analysis. There was also a significant correlation between the serum ECP level and the blood eosinophil count (r = 0.295, P = 0.000). No relationships of blood eosinophil count, and serum tIgE and sIgE levels with global severity of rhinitis as well as nasal obstruction symptom were found (all P > 0.05). CONCLUSIONS These results suggested that the severity of nasal obstruction was positively correlated with the duration of rhinitis and the levels of serum ECP in childhood persistent AR due to house dust mites, indicating the disease severity might be related to chronic inflammatory process.