Eradication of house dust mite from homes of atopic asthmatic subjects: a double-blind trial.

BACKGROUND House dust mite (HDM) allergens can accumulate to very high levels in homes. From the observed sensitivity of HDMs to heat and their allergens to steam, a novel treatment of furnishings has been developed. OBJECTIVE We sought to determine whether combined steam and heat treatment of home furnishings reduced asthmatic patients' bronchial hyperreactivity (BHR) and lowered HDM antigen loads. METHODS The homes of 30 asthmatic subjects aged 18 to 45 years were randomly allocated into 3 groups. In groups 1 and 2 mattresses and duvets were treated with hot air (110 degrees C), followed by steam and then heat again. All their carpets were steam cleaned. Group 2 also had a special ventilation system installed above each patient's bedroom. The homes of subjects in group 3 were sham treated. Neither patient nor laboratory staff was aware of the types of treatment. Der p 1 and 2 levels in the household dust from the lounge, bedroom carpet, and beds were determined before and after treatment and then at 6 and 12 months. BHR, measured by using histamine PD(20) values, was recorded during the 4-week run-in period and at 3, 6, 9, 12 months after treatment. RESULTS Active heat-steam treatment of homes caused a sustained reduction of Der p 1 (P =.003) and Der p 2 (P =.001) compared with no change in sham-treated group 3 homes. Patients whose homes were treated showed a 4-fold reduction in BHR at 9 months in group 1 and throughout the posttreatment period in group 2. No change was observed in the asthmatic subjects whose homes were not treated. These improvements were sustained for 12 months in the homes with bedroom ventilation units. CONCLUSIONS A single treatment of home furnishings reduced mite allergen load to below the risk level for sensitization and improved the asthmatic patients' BHR by 4-fold.