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To evaluate the effect of preventive measures 46 patients, all allergic to house-dust mites (Dermatophagoides spp.), were randomly allocated to a study and a control group. According to the patients' subjective recordings of symptom score and use of medicine, compared with the control group, the study group had improved. There was, however, no improvement when comparing the objective recordings of morning and evening peak flow and use of medicine, and it is concluded that the preventive measures in this programme are not very effective for patients allergic to house-dust mites. The reduction in indoor humidity in the study group was limited and, as a high indoor humidity is the cause of huge populations of house-dust mites in homes, it is emphasized that future programmes of preventive measures should focus more on damp problems, particularly those related to bad housing construction. [ABSTRACT FROM AUTHOR]

The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared. However, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapors) did not contain noticeable concentrations of house-dust mites kin the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, Al when this process is convenient to perform because of the low outdoor absolute humidity. [ABSTRACT FROM AUTHOR]

From a study of 98 typical Danish city apartments it was found that pyroglyphid and tarsonemid mites dominated the housedust acarofauna. Both groups of miles show a remarkable similarity in their occurrence and dependence on the microclimate. Room air humidities above 7 g water/kg dry air involved the highest densities. Below this limit only background contamination appeared. At least 14 distinct forms of carsonemid mites were found, with Tarsonemus floricolus Can. & Fanz., 1876 as the dominating species. As tarsonemid mites were found regularly rather than occasionally, it is suggested that these mites may be responsible for at least a part of the cases of housedust allergy that cannot be ascribed to the content of Dermatophagoides mites in the housedust. [ABSTRACT FROM AUTHOR]