House dust mites in Colorado.

Sixty-four samples of house dust from 16 long-established households in the Denver, Colorado area were analyzed for the presence of house dust mites (Dermatophagoides sp.). No mites were found in house dust from 12 of the sampled houses and small numbers (10 to 40 mites/g of house dust) were found from the other four. In an additional four houses which contained furniture recently imported from other areas, 100 to 360 mites/g of dust were found, and 2 years later up to 200 mites/g were still present. Twenty-eight percent of the mites in repeat collections from the latter homes were alive. The mite allergen content of house dust samples was analyzed by RAST inhibition against pooled sera from mite allergic patients. When dust from four long-established Denver households where no mites were found was employed, there was an average binding of 37.2%; with dust from the four Denver households with low levels of mites and no imported furniture, binding averaged 39.5%. In contrast, with house dust from four "positive control" homes in California and New York there was only 26.1% binding (P less than .005). The results of this study suggest that there are small numbers of nonintroduced house dust mites in some Denver houses, but that they contribute little mite antigen and are probably of minimal clinical significance in mite-sensitive patients. Large numbers of mites can be introduced with furnishings and may persist for at least 2 years. Similar small mite populations might be expected in other areas with comparable relative humidity.