Bronchial responsiveness to methacholine is increased in citrus red mite (Panonychus citri)-sensitive children without asthmatic symptoms

Background A recent investigation has suggested that citrus red mite (Panonychus citri, CRM) is a common sensitizing allergen among children living around citrus farms. Objective A cross-sectional survey was performed to evaluate the bronchial responsiveness to methacholine in CRM-sensitive children without asthmatic symptoms. Subjects and methods A total of 375 children living around citrus farms were enrolled in this study. There were 201 boys and 174 girls with a mean age of 12.5 (range 7-16) years. Each subject was evaluated by a questionnaire, a skin prick test with 13 common inhalant allergens including CRM, and a methacholine bronchial provocation test (MBPT). Results Positive rate of MBPT (PC₂₀-methacholine < 25 mg/mL) was higher in atopic rhinitic and atopic control children than in nonatopic rhinitic and nonatopic control subjects (41.3% and 33.3% vs 17.2% and 15.4%, respectively, both P < 0.05). Slope of dose-response curve (DRS, %/mg/mL) was higher in atopic rhinitic children than in nonatopic rhinitic, atopic control and nonatopic control subjects (14.3 ± 0.87 vs 9.4 ± 0.72, 10.0 ± 1.37 and 9.2 ± 1.51, P < 0.05, respectively). Both the positive rate of MBPT and the DRS were increased in children with positive skin response to CRM than in those without sensitization (48.2% vs 22.9%, P = 0.0001; 15.6 ± 1.26 vs 10.2 ± 0.65, P = 0.0001). Conclusion Bronchial responsiveness is increased in citrus red mite-sensitive children even if they have no asthmatic symptoms.