Predictors of house-dust-mite allergen concentrations in dry regions in Australia

Background: House-dust-mite allergen content differs between houses and is thought to be a function of the housing characteristics and furnishing choices that affect indoor microclimate and mite proliferation. The importance of these features may differ with regional climates. Methods: Concentrations of mite allergen were analysed as a function of housing features. Information on housing features was collected by questionnaire in 50 houses in two towns in a dry inland region of Australia. Mite allergen (Der p 1) was measured by ELISA in dust samples collected on five occasions over 2 years from beds and floors. Results: Der p 1 was detected in all houses. Many housing features did not influence mite allergen concentrations. However, the presence of evaporative cooling increased mite allergen by 3.34-fold in beds (P=0.007) and 3.94-fold in floors (P=0.003). Mite allergen was threefold higher in mattresses >5 years old, and synthetic and feather duvets tended to have higher and lower levels of mite allergen, respectively. Conclusions: In houses in dry, inland regions of Australia, evaporative cooling and older mattresses are associated with higher concentrations of mite allergen. Alternative forms of air conditioning to evaporative cooling may be useful for control of mite allergen in dry regions.