Sensitization to domestic mites in a cold temperate region

Factors favoring sensitization to house dust mites (HDM) were studied in a cold, temperate climate in northern Sweden. Sixty-five children previously found to react positively to a skin prick test (SPT) to HDM were included. The SPT to HDM was repeated, and serum IgE antibodies to D. pteronyssinus and D. farinae were determined. HDM, Euroglyphus maynei, Tarsonemus, or storage mites occurred in mattress dust samples from 23 of the 65 homes, and in 10 homes more than 100 HDM/g of mattress dust were found. Mites were more prevalent in mattress dust from the basement and ground levels than from the upper floors. Sensitization to HDM was strongly with the presence of domestic mites in mattress and floor dust. Previous longer stays in southern Sweden or Europe were also associated with present sensitization to HDM, and this was independent of occurrence of mites in the residence. The results indicate that HDM growth and potential for sensitization in cold, temperate regions is highly dependent on the microhabitat, and that sensitization to HDM should be possible to prevent in such climatic regions.