BACKGROUND: The decay of house-dust mite allergens is important for the outcome of avoidance measures for house-dust mite-allergic patients. OBJECTIVE: To quantify the stability of Der f 1 from mattress dust when exposed to domestic conditions. METHODS: Three samples of mattress dust were individually homogenized and divided into 64 subsamples. Mites were killed by freezing for 48 hours at -30 degrees C. The subsamples were exposed in eight homes, three storerooms, and one greenhouse, where temperature and relative humidity were recorded. Der f 1 was determined in extracts of subsamples (enzyme-linked immunoadsorbent assay) at 0, 3, 12, and 24 months. RESULTS: In the three samples of mattress dust, the initial concentrations of Der f 1 (mean +/- standard deviation; STD) were: 169 (12), 3.9 (0.4), and 31 (2.6) microg/g, respectively. Median half-life of Der f 1 in the mattress dust samples was 10 years in the exposure homes, 18 years in the store rooms, and 1.0 year in the greenhouse. No correlations among preserved Der f 1 and temperature, relative humidity, and absolute humidity in homes were found (Spearman rank correlation test). CONCLUSION: Natural decay of Der f 1, with an estimated half-life of 10 years at housing conditions, has no practical consequence in reducing allergen exposure. Therefore, avoidance measures should include an active removal of the allergens.
BACKGROUND: The decay of house-dust mite allergens is important for the outcome of avoidance measures for house-dust mite-allergicpatients. OBJECTIVE: To quantify the stability of Der f 1 from mattress dust when exposed to domestic conditions. METHODS: Three samples of mattress dust were individually homogenized and divided into 64 subsamples. Mites were killed by freezing for 48 hours at -30 degrees C. The subsamples were exposed in eight homes, three storerooms, and one greenhouse, where temperature and relative humidity were recorded. Der f 1 was determined in extracts of subsamples (enzyme-linked immunoadsorbent assay) at 0, 3, 12, and 24 months. RESULTS: In the three samples of mattress dust, the initial concentrations of Der f 1 (mean +/- standard deviation; STD) were: 169 (12), 3.9 (0.4), and 31 (2.6) microg/g, respectively. Median half-life of Der f 1 in the mattress dust samples was 10 years in the exposure homes, 18 years in the store rooms, and 1.0 year in the greenhouse. No correlations among preserved Der f 1 and temperature, relative humidity, and absolute humidity in homes were found (Spearman rank correlation test). CONCLUSION: Natural decay of Der f 1, with an estimated half-life of 10 years at housing conditions, has no practical consequence in reducing allergen exposure. Therefore, avoidance measures should include an active removal of the allergens.