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House Dust Mites

Veröffentlicht am: Monday, 19. November 2007

House dust mites do not appear as a result of insufficient hygiene, but are in fact natural cohabitants of ours. They beloHouse dust mites do not appear as a result of insufficient hygiene, but are in fact natural cohabitants of ours. They belong to the arachnid family. Worldwide, there are approximately 150 different species, and they measure 0.1 to 0.5 mm in size.ng to the arachnid family. Worldwide, there are approximately 150 different species, and they measure 0.1 to 0.5 mm in size.

House dust mites enjoy ideal living conditions at room temperatures of 25 to 30 °C and a relatively air humidity of 65 to 80 percent. At a relative air humidity of less than 50 percent they die off.

The mites feed primarily on flakes of human skin and animal dander, and also mildew. They live in beds, carpets and upholstered furniture, because this is where they find suitable living conditions. The highest concentration of mites is usually to be found in pillows. Each day, the average human loses approximately 1.5 g of dead skin cells, mostly in bed. During the night, he also emits between 250 and 400 ml of moisture. A pillow which has not been washed for years contains up to 400,000 mites. The proportion of living and dead mites in a pillow like this can account for roughly 10 percent of its total weight.

A house dust mite produces approximately 20 faeces a day, and over the course of its two to four months of life as a mite, this equates to 200 times its own body weight. It is the faeces which trigger an allergy to house dust mites. One teaspoonful of bedroom dust contains an average of 1,000 mites and 250,000 faeces. The faeces decompose into an ultra-fine dust (one particle measuring approximately 35 µm), which is dispersed into the air by movements in the environment and then breathed in.

Allergic complaints triggered by mite faeces include itching and watery eyes (conjunctivitis), sneezing attacks, a runny or blocked up nose, skin reactions and, less frequently, coughing or a ringing in the ears, but sometimes also breathing difficulties and allergic bronchial asthma. If the complaints are more severe after getting up in the morning than they are during the day, this usually indicates the presence of a house dust mite allergy.