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The House Dust Mite
Dermatophagoides pteronyssinus

We live surrounded in filth. Sorry, but it's a fact. All humans shed about 5-10 grams of dead skin each week. About 80% of the material seen floating in a sunbeam is actually flakes of skin.

House dust mites are nearly universal in occurrence - a typical bed mattress may have contain anything from 100,000 to 10 million mites. Ten percent of the weight of a two year old pillow may be composed of dead mites and their droppings. Carpets and household upholstery also support high mite populations. What do house dust mites eat? Human and animal skin flakes (Dermatophagoides - "skin eater"). So in some ways house dust mites are a good thing - they help stop us drowning in our own filth.

House dust mites are 0.2-0.3 mm long and translucent. Because of this, they are essentially invisible to the unaided eye. A dust mite's tough, translucent cuticle has deep striations that can be seen from both the dorsal and ventral views, with long setae (hairs) extending from the outer margins of the body and shorter setae on the rest of the body. There have eight legs, no eyes, no antennae and mouthparts in front of their bodies (resembling a head):

So why are we interested in dust mites?

House dust is a strongly allergenic material because it is usually heavily contaminated with the faecal pellets and skins of Dermatophagoides. Some estimates are that dust mite allergens may be a factor in 50-80% of asthmatics, as well as in eczema, hay fever and other allergic conditions. Exposure of the skin or respiratory tract to proteinases is frequently associated with allergic sensitization. The wheeze-inducing proteins are digestive juices from the mite gut which are quite potent. The proteolytic activity of Der p I, the group I allergen of Dermatophagoides pteronyssinus, may influence the allergenicity of mites. The mites in this video aren't just any only mongrels, oh no! They are pedigree mites lovingly bred on a diet of baker's yeast and beard shavings for research purposes.

Exposure to the mites in the first, crucial year of life can trigger a lifelong allergy. There is no cure, only prevention - controlling house dust mite populations - focusing on dust control, to reduce the concentration of dust-borne allergens in the living environment by controlling both allergen production and the dust which transports it:

However, to be effective, measures may need to reduce the house dust mite pollution 10 to 100-fold, not easily achieved in practical terms. It's important not to become so obsessed with mites, germs and dirt that normal life is impossible.

If you or a member of your family has asthma or any other allergy, consult your Doctor.

 


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