Indoor environmental factors associated with house-dust-mite allergen (Der p 1) levels in south-eastern Australian houses.

Abstract

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. 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. 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. Avoiding wool bedding and replacing inner-spring mattresses with foam could substantially reduce bed allergen levels.