House dust mites produce well-known allergens for asthma and allergy among children. To study house dust mite allergen exposure level in northeast China and characterize its association with indoor environmental factors and cleaning habits, we inspected 399 homes in Tianjin area and collected dust from mattresses. Dermatophagoides farinae (Der f) and Dermatophagoides pteronyssinus (Der p) were detected by the enzyme-linked immunosorbent assay (ELISA) method. The medians of total allergen concentrations for spring, summer, autumn, and winter were 524 ng/g, 351 ng/g, 1022 ng/g, and 1010 ng/g.