ABSTRACT
BACKGROUND: House dust mites have been considered the most important source of allergens for humans. These allergens have been encountered at different indoor sites, mainly on mattresses and pillows. OBJECTIVE: To evaluate the number and different specimens of mites on Brazilian bunk-bed mattresses. METHODS: Dust samples were collected once using a standardized method on the upper mattress surface (US) and lower mattress surface (LS) (bed frame also included in the latter) of 58 mattresses. RESULTS: The total number of mite bodies on the LS was 3.5-fold higher than on the US, with a mean concentration of 932 mites per gram of fine dust (mites/g) on the US (range, 0-3,375 mites/g) and 3,254 mites/g on the LS (range, 125-14,500 mites/g) (P < .001). Additionally, the number of house dust mite bodies on the LS was 2.4 higher than on the US (P < .001); the mean concentration was 750 mites/g on the US (range, 0-2,875 mites/g) and 1,816 mites/g on the LS (range, 0-10,875 mites/g). Approximately 91% (n = 52) of the US and all LS dust samples had more than the limit of 100 mites/g. The most frequent family was Pyroglyphidae in both mattress surfaces, with Dermatophagoides pteronyssinus the most important species found. Storage mites, including Glycyphagidae (P < .001), Acaridae (P < .001), and other families (P < .001), also showed significant differences in the number of mites between both sample counts. CONCLUSIONS: This study shows a significant difference in US and LS mite counts, with higher counts on the LS. Mite allergen avoidance should include the LS and bed frame as potential targets.