The dust mite is an organism that has been sharing its habitat with humans for several centuries. There is a hypothesis that they were originally introduced into human
homes with poultry down and feathers in pillows and featherbeds, or with agricultural products.
Later on mites were transferred from one accommodation to another on clothes and other items. The dust mite is so small that it is impossible to see with the naked eye. But their number around us is just huge, from a hundred to several thousands in one gram of dust, and from 200 to 500 million in a double bed.
Dust mites live in mattresses, pillows, bedding, carpets and upholstery, but their favorite place in any house is the bed of the house owners. There they feed on dead cells of human skin and the microflora (bacteria and fungi) living on them.
One gram of dead skin cells is enough to support thousands of dust mites. Besides, the human body creates optimal conditions for their development in the bed: the temperature of about 25 ºC and the humidity of 70%. A mattress used for 3 to 5 years without special treatment may owe up to 5% of its weight to dust mites and their faeces, dead cells of human skin, etc.
Also, mites are a part of domestic dust. Their excrements (faeces) sized 10 - 40 microns accumulate in the dust, and rise in the air with it, without settling for 10 - 20 minutes. When such air is inhaled, the excrements get to the mucous membranes of the nasopharynx and quickly are dissolved, further provoking allergic reactions.
Allergy is visibly manifested as dermatitis, allergic rhinitis or bronchial asthma. Of course, allergy develops not in everyone, but in people with a predisposition to this disease and with suppressed immune system.