Dust mites: using data from an intervention study to suggest future research needs and directions

Dermatophagoides farinae (Der f 1; referred as Der f hereafter) and D. pteronyssinus (Der p 1; referred as Der p hereafter) are common allergy-causing mites found in homes worldwide. Mites are more prevalent in humid climates, but are rare or absent in drier climates. Levels of dust mite sensitivity have been reported between 48% and 63% for asthmatic children. Dose-response relations between levels of dust-mite exposure and sensitivity have been reported; yet, relatively high levels of dust mite sensitivity (50%-60%) have been found in populations exposed to concentrations below the proposed cut-point sensitization concentration of 2 microg dust mite per gram of dust. A meta-analysis of 49 trials involving 2733 patients found that interventions for dust mite-control did not result in any clinical benefit to mite-sensitive asthmatics. We assessed the impact of replacing old mattresses with dust-mite resistant mattresses on dust-mite levels, and to a more limited extent, on health outcomes. Replacement mattresses were provided to 44 asthmatic children residing in public housing in inner city Boston, Massachusetts. At baseline, we found concentrations to exceed the cut point of 2 microg g(-1) in only 9% of beds for Der p and 16% for Der f. Only 7% of beds for Der f and 5% for Der p exceeded 10 microg g(-1). Dust-mite allergy levels were high in these asthmatic children (54% for Der f and 62% for Der p) despite low baseline mattress levels. Our intervention reduced Der p (p = 0.026) and Der f (p < 0.001) below their low starting levels. Investigations are needed that (1) evaluate the reduction of dust-mite levels below the suggested cutpoints for sensitization and exacerbation; (2) assess the impact of reduction of multiple antigens; (3) assess exposure to dust mites outside of the home; and (4) test bundled interventions.