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The prevalence of allergic diseases in Saudi Arabia is known to be increasing. Indoor allergens appear to play an important role in allergic sensitization and manifestations of symptoms. In order to identify and quantify common house dust mites, we investigated specific indoor determinants of some dust mite allergens and their concentrations in settled house dust samples in patients and control samples from coastal and non-coastal cities. A total of 560 house dust samples were collected from diagnosed respiratory allergic patients (n=164) and control homes (n=396) from eleven cities including coastal and non-coastal regions. The dust samples were collected in sterile plastic (ziploc) bags by 5 min vacuuming of the required areas. Der p1 from Dermatophagoides pteronyssinus, Der f1 from D. farinae, and Blo t5 from Blomia tropicalis allergens levels were quantified by dust extraction and ELISA using monoclonal antibodies from Indoor Biotechnologies, (Cardiff – UK). The analysis of data revealed comparatively higher concentration levels of all 3 allergens mentioned above in coastal cities compared to non-coastal ones. The patients’ homes showed overall higher level of Der p1 (25%) while in control homes both, Der f1 (25%) and Blo t5 (17%) were higher. Coastal cities constituted higher level of all HDMs compared to non-coastal cities. Der p1 was found to be higher in patient homes compared to Der f1 and Blo t5 in control homes. Keywords: Asthma, House Dust Mite, Indoor Allergens, Allergic Disease, Coastal Cities.