Seasonal fluctuations of Dermatophagoides mite population in house dust.

To evaluate seasonal fluctuations of Dermatophagoides species (sp.) in residential houses in Mie Prefecture, Japan, we employed the ELISA inhibition method with rabbit polyclonal antibody to eggs and adult mites. House dust accumulated for seven days in vacuum cleaners was collected from 14 houses of atopic patients every month for one year. The one-week-dust samples weighed from 2.5 to 117 g (mean 35.9 g). The density of Dermatophagoides spp. in the dust samples were 5 to 755 mites per gram (mean 109). During one week, 100 to 20,400 (mean 4,200) mites of Dermatophagoides sp. were collected. Among 142 samples in one year, 50 (35.2%) contained more than 100 mites per gram, which is a critical number for atopic symptoms. From December to February, 12 (34.5%) out of 35 samples contained more than 100 mites per gram. These results suggest that Dermatophagoides sp. have become a year-round allergen in Japan.