Quantities of household dust vary enormously depending on where the house is located, the climate, altitude, the time of year, etc. They also vary from house to house, for example a farm is different from a city flat, and within the same house from room to room.

There is however one thing that never varies: household dust is a complex reservoir of allergens. The main allergen is related to the house dust mite.

Dust Mites

Mites or acarids are tiny spider-like creatures only about 0.3 millimetres long and are therefore invisible to the naked eye.

House dust mites feed on human scales or flakes which shed from the skin. They are found mainly in bedding (pillows, mattresses, feather duvets, etc.) because this is where we lose the most dead skin as our skin rubs against the sheets. Feeding on shed skin is not enough for these mites, they also feed on a microscopic fungus (mould) which grows mainly on mattresses.

To complete this delightful picture, it may be interesting to know that people with mite allergy are not allergic to the mites themselves, but to their droppings. House dust mite excreta seems to be highly allergenic.

House dust mites are much more numerous in bedding than on the bedroom floor. One gram of dust taken from a mattress could contain anywhere from 2,000-15,000 of them!

The temperature of between 20-30°C and relative humidity (dampness) created by your body whilst you are asleep in bed, provides ideal conditions for these unsavoury little creatures to reproduce; as well as ideal growing conditions for the mould on which they feed.