Mites in house dust in the Stockholm area.

Today there is no doubt that mites (and especially species within the Pyroglyphidae family: Dermatophagoides pteronyssinus and Dermatophagoides farinae) are an important agent in dust allergies. The author reports on a study of the occurrence of mites in house dust in the environment of allergic persons in the Stockholm area. 201 private homes, 13 farmers' houses and two hospitals have been studied. In 12% of the homes several different types of mite were found in dust in relatively small numbers, while pyroglyphids occurred in only 1.5% of the dwellings. The frequency of mites in dust from farmers' homes was three times higher and that of pyroglyphids ten times higher than in other dwellings. Mites were most often found in floor dust and very infrequently in bed dust. All hospital beds were free from mites; in floor-dust samples from a hospital for long-term therapy several species of mite were found. The author draws the conclusion that the conditions of climate and humidity within the geographical area studied are adverse to the development of an allergologically significant mite population in indoor dust, but that small numbers may spread from potted plants, work premises and outdoor flora.