Present situation of house dust mites in Dakahlia Governorate, Egypt.

House dust mites are common inhalant allergens, which can precipitate atopic disease episodes. The present study revealed presence of four mites. These are Dermatophagoides farinae, D. pteronyssinus, Acheles gracilis and Ornithonyssus bacoti. Population densities of different live adult mites were investigated in different house habitats. In urban houses, pyroglyphid mites were the predominant in bedrooms and D. farinae was the most abundant. A. gracilis was more abundant in living rooms followed by D. farinae then D. pteronyssinus. A. gracilis was the most prevalent in kitchens. While in rural houses, O. bacoti was the most abundant species followed by pyroglyphid mites. Since Dermatophagoides species and A. gracilis were present in numbers high enough to allow their ecological consideration, their seasonal abundance in urban bed-rooms was investigated and revealed that both D. farinae and D. pteronyssinus have two peaks of abundance, one slightly higher in spring and the second in autumn. A. gracilis has two peaks but the higher occurred in autumn and the second in spring.