The Melbourne House Dust Mite Study: Eliminating house dust mites in the domestic environment,☆☆,,★★

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Abstract

Background: Hypersensitivity to house dust mite allergens is associated with increased asthma morbidity. Asthma severity appears to be related to the degree of mite allergen exposure. Short-term studies suggest that complete avoidance reduces disease severity. Objective: The study was designed to assess the effect of different mattress covers and floor coverings on mite allergen concentrations in the homes of mite-sensitive children with asthma in the city of Melbourne, Australia. Methods: Mite allergen Der p 1 concentration was measured on mattress covers, mattress surfaces, and carpeted and uncarpeted floors in 107 dwellings; and measurement was performed on three occasions over a 5-month period. After the first sampling, all mattress covers and impermeable encasements were permanently removed. Results: The initial geometric mean concentrations of Der p 1 (micrograms per gram of fine dust) from the surfaces of sheepskin, wool, and cotton mattress coverings were greater 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 concentrations 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 concentration of Der p 1 in uncarpeted rooms was below the reported threshold for sensitization and significantly less than that in the adjacent carpeted room. Conclusion: In homes of children with asthma, “asthmogenic” 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 below the reported threshold for sensitization. (J Allergy Clin Immunol 1997;99:323-9.)

Section snippets

Conduct of study

This study was conducted between winter (July) and late spring (November 1991).

One hundred seven children with moderately severe asthma (median dose of inhaled steroids, 600 μg/day), 71 boys with a median age of 8 years (range, 4 to 17 years) and 36 girls with a median age of 9.3 years (range, 4 to 16 years) who were all under the care of a single physician, were enrolled in the 5-month study. All had demonstrated skin prick test reactivity (wheals >6 mm) to an extract of D. pteronyssinus

Patient numbers

One hundred seven homes were entered into the study. Seven were withdrawn after the first visit, and 12 were withdrawn after the second. Among these withdrawals, 11 families moved, five were unwilling to follow the trial's protocol, and three were difficult to contact for further sampling for logistical reasons. Consequently, 88 dwellings were available for analysis at the end of the study.

Meteorologic data

The study was conducted within 15 km of the central business district of Melbourne, a capital city in

DISCUSSION

Two major findings from this study have public health implications in terms of controlling house dust mite allergen exposure. First, the concentration of Der p 1 in these domestic dwellings of mite-sensitive patients with asthma are among the highest in the world, being similar to those from Sydney18 and some dwellings in the United Kingdom 19, 20 but up to 100 times higher than levels in Sweden,21, 22 The Netherlands, 23, 24 Canada,25 and other parts of Australia.26 Second, the only dwellings

Acknowledgements

We thank Tina Colgan, Carmel Swingler, Joan Sedmak, Department of Allergy; Patty Chondros, Clinical Epidemiology and Biostatistics Unit; the staff of Biomedical Engineering, Royal Children's Hospital, Melbourne; and Karen Krska, Princess Margaret Hospital, Perth, Western Australia, for their assistance. Dr. Martin Chapman, University of Virginia, provided monoclonal antibody kits for Der p 1.

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  • Cited by (0)

    From aDepartment of Allergy, Royal Children's Hospital, Parkville; bDepartment of Medicine, University of Western Australia; cDepartment of Microbiology, University of Western Australia; dClinical Epidemiology and Biostatistics Unit, Royal Children's Hospital; eUniversity of Melbourne Department of Paediatrics; and fClinical Immunology, Royal Children's Hospital.

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    Supported by a grant from The Victorian Health Promotion Foundation, Melbourne, Australia.

    Reprint requests: David J. Hill, FRACP, Director, Department of Allergy, Royal Children's Hospital, Parkville, 3052 Australia.

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