Role of environmental exposure to spider mites in the sensitization and the clinical manifestation of asthma and rhinitis in children and adolescents living in rural and urban areas

Background Spider mites such as the citrus red mite and the two-spotted spider mite have been demonstrated to be important allergens for fruit cultivating farmers. Objective To evaluate the role of environmental exposure to spider mites in the sensitization and the clinical manifestations of asthma and rhinitis in children and adolescents living in urban and rural areas. Methods A total of 16 624 subjects (aged 7 to 18 years) living in urban (metropolitan and non-metropolitan) and rural areas (apple orchards and citrus orchards) in Korea were evaluated by questionnaire and skin prick test for 11 common aeroallergens, including citrus red mite (CRM) and two-spotted spider mite (TSM). Results The positive skin response rates to TSM were 4.2% of 1563 metropolitan subjects, 3.8% of 5568 non-metropolitan subjects and 6.5% of 1464 subjects living nearby apple farms, and that to CRM 15.6% of 8029 living nearby citrus farms. The prevalence of current wheeze and rhinitis as reported on a questionnaire was higher among those with a history of visiting fruit farms once or more per year than among those without it (10% vs. 7.1%, 32.8% vs. 26.7%, for wheezing and rhinitis, respectively). Among those with wheezing or rhinitis, the positive skin responses to TSM or CRM were also higher among those with a history of visiting fruit farms than among those without one (11.2% vs. 6.6%, 13.0% vs. 6.6%, respectively), although the positive skin responses to house dust mites were similar in the both groups. Conclusion Spider mites are common sensitizing allergens in children and adolescents exposed to them, and environmental exposure to these mites may represent an important risk factor in the sensitization and the clinical manifestations of asthma and rhinitis in children and adolescents living in rural and urban areas.