Indoor environmental factors associated with house‐dust‐mite allergen (Der p i) levels in south‐eastern Australian houses

BACKGROUND: Eighty households in the Latrobe Valley, Victoria, Australia, were sampled for house-dust-mite allergen (Der p 1). Allergen levels vary greatly between houses within climate regions. The reasons for this are not well understood. METHODS: House-dust-mite allergen samples were collected on six occasions between March 1994 and February 1995. All participating households contained at least one child between 7 and 14 years with a total of 148 subjects, 53 of whom were asthmatic. A detailed house survey was performed during every sampling visit, and a dwelling questionnaire was completed. Relative humidity was measured at the time of sample collection. RESULTS: The median bed allergen level was 30 microg/g during the first sampling period. Significantly higher allergen levels were associated with wool bedding and inner-spring mattresses (P < 0.001). As estimated from a multiple linear regression model, up to 70% reduction in bed allergen levels may be achieved by avoiding wool bedding and inner-spring mattresses. Other risk factors for high allergen levels included high indoor relative humidity, presence of substantial visible mould growth, brick cladding, and concrete slab foundation of the house. CONCLUSIONS: Avoiding wool bedding and replacing inner-spring mattresses with foam could substantially reduce bed allergen levels.