Distribution of house dust mites, booklice, and fungi in bedroom floor dust and bedding of Japanese houses across three seasons

This study surveyed bedrooms and bedding in 38 dwellings in Tokyo and nearby prefectures to determine the distribution of allergenic organisms (house dust mites, booklice, and fungi) in house dust and their variations among three seasons: spring, summer, and autumn. A total of 8,783 American house dust mites (Dermatophagoides farinae) were isolated from bedding and 30,927 were isolated from floors. A total of 428 European house dust mites (Dermatophagoides pteronyssinus) were isolated from bedding and 505 were isolated from floors. A similar tendency was observed in mite antigens. There was significantly more Der f 1 than Der p 1. The proportion of Japanese dwellings inhabited by D. farinae has become extremely high in recent years. A large number of booklice were also isolated: 213 from bedding and 1,628 from floors. D. farinae and booklice tended to be larger in number in summer and autumn than in spring. There were more mite antigens and fungi from floors in summer and autumn than in spring but the number of those from bedding did not significantly differ by season. Significantly fewer D. farinae and booklice were isolated from flooring than from carpets or tatami mats. Furthermore, the number of D. farinae and booklice from floors tended to decrease significantly with the frequency of cleaning the floors. With regard to fungi, Aspergillus, Cladosporium, and yeasts were isolated frequently. Significantly more hydrophilic fungi (cfu/total dust) tended to be isolated from bedding than from floors.