Sensitization to dust mites in children with allergic rhinitis in Singapore: does it matter if you scratch while you sneeze?

BACKGROUND: Previously published data established Blomia tropicalis, as the major source of allergic sensitization in asthmatic children in tropical Singapore. Objective To define the prevalence, clinical characteristics and risk factors of species-specific mite sensitization in paediatric allergic rhinitis (AR) patients in this unique environment.

METHODS: We performed a prospective evaluation of newly diagnosed AR patients, from 1 May 2003 to 30 April 2004, from the otolaryngology and allergy outpatient clinics of the Kendang Kerbau Children's Hospital in Singapore. Patients included in the study showed evidence of sensitization to at least one respiratory allergen source and completed a detailed questionnaire. Relative risk of sensitization and associated risk factors were calculated using logistic regression analysis with the forward stepwise model. Multivariate regression analysis was performed to adjust for confounding interactions. Continuous values were compared using anova, SPSS 9.0 for Windows (SPSS Inc., 1999).

RESULTS: One hundred and seventy-five patients were included, 119 (68%) males, 142 (81%) Chinese, age mean 7.9 years (range 2-16). Sixty-eight patients (39%) reported a concomitant diagnosis and/or clinical complaints of bronchial asthma and 84 (48%) of atopic dermatitis. Skin prick test results were positive for traditional house dust mites (Dermatophagoides pteronyssinus. and D. farinae mix) in 85% of patients and for B. tropicalis in 62%. Overall mite sensitization was 98%, household pets 10%, moulds 9% and food proteins 12%. By far the single most significant factor associated with Dermatophagoides sensitization in this group was the presence of allergic eczema (odds ratio (OR) 31.8%, 95% confidence interval (CI) 3.6-285, P=0.002). Allergic eczema was negatively associated with B. tropicalis sensitization (OR 0.26%, 95% CI 0.14-0.5).

CONCLUSIONS: Children with AR and concomitant atopic dermatitis show a preferential sensitization to the Dermatophagoides mites. In our population, B. tropicalis sensitization is more prominent in children with pure respiratory allergy.