Canadian Allergy, Asthma and Immunology Foundation

Fondation canadienne d'allergie, d'asthme et d'immunologie
 caaif@rcpsc.edu

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ALLERGY TO HOUSE DUST MITES

House dust mites are natural inhabitants of our surrounding environment. The presence of house dust mites does not indicate a lack of cleanliness. House dust mites do not pose a problem for most people, but they certainly do for people who are allergic to them. House dust mites avoid contact with humans and are not known to transfer any diseases. They are not visible to the naked eye. They live in house dust and feed on its various particles, especially on the flakes from human or animal skin contained in the dust.  The average adult human loses up to 1.5 grams of skin particles per day. This amount is sufficient for the nourishment of house dust mites, and even tides them over during periods in which rooms are not entered. In addition to this food, they also take in material of other origin, such as pieces of fiber and feathers. The development and propagation of house dust mites is dependent upon relative humidity and temperature. They thrive at temperatures between 68-84 degrees F (20 to 30 degrees C) and a relative humidity of 65 to 80%. This moderate, moist climate is prevalent in our area from May to October.  This is also the period in which house dust mites mature and breed.

House dust mites prefer to live in mattresses, upholstery, rugs, carpets, quilts, pillows, and almost all textile items (including children's textile toys). Sleeping areas of house pets are also favorite spots. House dust mite allergies are rarely caused by the house dust mites themselves, but rather by their excrement (feces). What makes matters worse, the excrement and the allergens contained therein are present all year long-as opposed to pollen allergens which only induce allergic reactions during pollen seasons. Constant exposure to mite allergens can lead to chronic (long-term) illnesses. The finally grained excrement breaks down to an extremely fine powder. This powder sticks to the surrounding materials, such as the fiber structure in carpets and upholstery. This powder becomes airborne when the carpet or rug is walked on, by sitting down on or rising from upholstery, shaking out blankets, and airing out rooms. The excrement problem can only be solved by eliminating the house dust mites.