THE MELBOURNE HOUSE-DUST MITE STUDY - ELIMINATING HOUSE-DUST MITES INTHE DOMESTIC ENVIRONMENT

Background: Hypersensitivity to house dust mite allergens is associate d with increased asthma morbidity. Asthma severity appears to be relat ed to the degree of mite allergen exposure. Short-term studies suggest that complete avoidance reduces disease severity. Objective: The stud y was designed to assess the effect of different mattress covers and f loor coverings on mite allergen concentrations in the homes of mite-se nsitive children with asthma in the city of Melbourne, Australia. Meth ods: Mite allergen Der p 1 concentration was measured on mattress cove rs, mattress surfaces, and carpeted and uncarpeted boors in 107 dwelli ngs; and measurement was performed on three occasions over a 5-month p eriod. After the first sampling, all mattress covers and impermeable e ncasements mere permanently removed. Results: The initial geometric me an concentrations of Der p 1 (micrograms per gram of fine dust) from t he surfaces of sheepskin, wool, and cotton mattress coverings were gre ater than those from the surfaces of impermeable mattress encasements (116, 113, and 19 vs 0.4) (p < 0.001); corresponding concentrations on the underlying mattresses were 142, 38, 20, and 0.6, respectively (p < 0.05 to 0.001). At the end of the study these mattress surface conce ntrations were 79, 65, 9.7, and 3.1, respectively. In 24 dwellings an uncarpeted room was adjacent to a carpeted room. At each visit the con centration of Der p 1 in uncarpeted rooms was below the reported thres hold for sensitization and significantly less than that in the adjacen t carpeted room. Conclusion: In homes of children with asthma, ''asthm ogenic'' concentrations of Der p 1 were found on nonencased mattresses and carpeted floors, but the use of impermeable mattress encasements and carpet exclusion were associated with concentrations of Der p 1 be low the reported threshold for sensitization.