Residential characteristics influence Der p 1 levels in homes in Melbourne, Australia

Exposure to house dust mite (HDM) allergens is an important risk factor for childhood asthma. Knowledge of environmental determinants of HDM allergen levels is essential before designing rational avoidance measures.

To investigate the effect of domestic characteristics on HDM allergen (Der p 1) levels in Melbourne homes.

Dust was collected from bed and floor of the bedrooms in 485 houses over a period of one year. Dust was analysed for Der p 1 levels using an enzyme-linked immunosorbent assay. Temperature and relative humidity were measured at the visit. Details of residential characteristics were collected using a questionnaire. Statistically significant predictors of Der p 1 levels (P < 0.05) were identified using multiple linear regression.

High levels of Der p 1 were observed in the floors (geometric mean 17.2 microg/g fine dust) as well as in the beds (geometric mean 20.3 microg/g fine dust). Der p 1 levels in the floor dust were significantly lower in winter and spring. They were higher in houses built before 1980 and those with central heating, weather board walls, damp bedrooms or fitted old wool carpets. Der p 1 levels in bed dust were significantly higher in houses built before 1980, with wooden floors built on stumps, with high relative humidity, with visible mould in the room, in beds with an old mattress or in beds without a quilt.

We would encourage construction of homes without carpets, wooden floors on stumps or weather board walls.