House dust mites (HDM) are the main source of aeroallergens worldwide, yet epidemiological differences between socioeconomic factors in association with this medical condition have not been studied in the south region of Brazil. To assess the prevalence of HDM in two socioeconomically distinct populations of patients with allergic asthma or rhinitis, the differences between samples from houses of high-income families and low-income families were analyzed. Mite samples were collected between July and December 2015, in Porto Alegre, Brazil. The HDM were Dermatophagoides pteronyssinus and Dermatophagoides farinae (Hughes; Acari: Pyroglyphidae). Also, other non-pyroglyphid house mites were identified in dust samples: Tyrophagus putrescentiae (Schrank; Acari: Acaridae), Chortoglyphus arcuatus, and Cheyletus malaccensis. Identification of species was performed through morphological keys with a stereomicroscope and a phase optical microscope. A total of 104 homes was evaluated (low-income group: n = 53; high-income group, n = 51). We found a total of 721 mites, representing 11 species, in 93 (89%) houses. In the remaining houses, no mites were found. We observed no significant differences of species composition between the groups studied. However, the number of mites was significantly higher in the low-income group (P < 0.001). D. pteronyssinus was the predominant species detected, with 286 mites (39.6%). D. farinae was not detected in any sample. Our results show that living-rooms from low-income families present higher numbers of HDM.