Seventy-three patients (52 females and 21 males) with suspected itching dermatitis caused by house-dust mites admitted to our hospital during the period of June 1984 to December 1991. Survey of the mites in house-dust collected from the residences of all patients was carried out to clarify the precise relationship between itching dermatitis and causative mites. The patients were more in female (71.2%) than in male (28.8%), and the highest incidence was observed in female in forties (19.2%). The mite infestation occurred most in August and September in every year. Eighteen mite species in 11 families were found in 56 (76.7%) out of 73 cases. The dominant species were Dermatophagoides farinae (47.9%), D. pteronyssinus (27.4%), Haplochthonius simplex (26.0%), Chelacaropsis moorei (24.7%), Cosmochthonius reticulatus (21.9%), Laelaps spp. (11.0%), Dermanyssidae spp. (7.7%), Cheyletus fortis, Tyrophagus putrescentiae and Hirstia domicola (6.8% each). In 32 (43.8%) out of 73 cases, 5 mite families such as Cheyletidae (34.2%), Laelapidae (11.0%), Dermanyssidae (7.7%), Macronyssidae (Ornithonyssus bacoti) (2.7%) and Pyemotidae (1.4%) were confirmed. Therefore, it reveals that the itching dermatitis found in 32 patients were caused by the mites inhabiting in house-dust
