Purpose of the Study
The investigators evaluated the effectiveness of dust mite control measures in bedrooms of mite-allergic children with asthma.
Eighty-five children with moderate asthma requiring chronic inhaled medication were selected. All were skin test-positive to the dust miteDermatophagoides pteronyssinus.
Samples of house dust were obtained on 10 visits over a 16-month period. Locations sampled included child's and parents' bedroom floors and child's mattress or mattress encasement. Any existing encasements were removed on visit 1. During visit 3, investigators encased all mattresses and began interventional measures, which were repeated at each subsequent visit. Encasements were wiped down, and carpets and floors were washed: uncarpeted floors with “anti-mite” shampoo, and carpets with either “anti-mite” or placebo shampoo. Subjects washed bed linens weekly, and were told not to vacuum 1 week before each visit. Samples with <10 g dust were not analyzed.
Although not insignificant, dust mite antigen from uncarpeted floors remained low throughout the study. Neither shampoo diminished levels of Der p 1 in carpeting; levels were similar in untreated parents' bedrooms, and were >10 μg Der p 1/g dust, the proposed threshold for provoking symptoms in sensitized individuals. The use of encasements substantially lowered concentrations of Der p 1 recovered from mattresses after one visit (28.4 to 4.2 μg/g). Of all samples from mattress encasements, 96% had <10 μg Der p 1/g dust. In fact, many samples from uncarpeted floors and mattress encasements had insufficient dust to examine.
Mattress encasements and absence of carpeting were associated with low concentrations of dust mite antigen.
Investigators only measured one dust mite associated protein. Nonetheless, the levels found after implementing these measures were generally below the threshold for provoking asthma, although not low enough to prevent allergic sensitization. Controlling indoor humidity may reduce levels further. The authors in this study did not correct for air conditioning by measuring indoor humidity; this may explain the lack of correlation between mite allergen levels and seasonal variation in humidity. Parents must implement effective measures and not waste time and money on air cleaners, excessive vacuuming, and housecleaning which provide little, if any, benefit in reducing dust mite antigen exposure. Strict examination of data from controlled studies help us discern fact from fiction and help us guide parents around often a wealth of misinformation presented by well-meaning friends and family or, in some cases, those with proprietary interests.