Household dust

Quantities of household dust vary enormously depending on where the house is located, the climate, altitude, the time of the year, etc. They also vary with the type of house (a farm is different from a city flat) and even within the same house (e.g. between the bathroom and bedroom).

There is however one thing that never varies: household dust is a complex reservoir of allergens, the most important being the house dust mite. Other allergens found in dust include animal allergens, moulds, cockroach and food allergens.

House dust mites

Mites (or acarids) are tiny spider-like creatures, only about 0.3 millimetres long that live and feed on substances present in the dust. Being so small, they are invisible to the naked eye. Two species living in household dust are very important in respiratory allergies: Dermatophagoides pteronyssinus and Dermatophagoides farinae.

Dermatophagoides mites feed on human skin cells that are shed from the skin (hence their complicated Latin names dermato = skin, phagos = to eat). They are found mainly in beds (pillows, mattresses, etc.) because this is where we lose the most skin cells (our skin rubs against the sheets). Feeding on shed skin is not enough for these mites. They also feed on a microscopic fungus (mould) that mainly grows on mattresses.

Another reason that makes the bed an ideal place for mites to grow: when you sleep, the temperature (between 20 - 30°C) and humidity (dampness) created by your body, provide ideal conditions for these unsavoury little creatures to reproduce. As they cannot drink, house dust mites die in dry conditions - but dead house dust mites are still allergenic and need to be removed.

House dust mite allergens cause symptoms all year round; they are perennial allergens. However, the concentration of house dust mites and mite allergens is highest during the spring and autumn when the weather conditions (warm and humid) are ideal for their breeding.

Symptoms: Allergy to house dust mites is expressed mainly as asthma and rhinitis. It can also cause allergic conjunctivitis and atopic dermatitis (eczema). Flare-ups usually happen just after the sufferer wakes-up. Symptoms tend to be worse in spring and autumn when the air is moist and warm.

Since mites cause the symptoms in mite allergy sufferers, elimination of them would seem to be a very useful approach for reducing symptoms. Unfortunately, it is extremely difficult to eradicate mites completely. However, it is possible to reduce the allergen levels to below the threshold that triggers symptoms. Creating a virtually “mite-free” house is not easy; it requires diligent measures and 100% commitment. Going just “half way” will probably have no effect on your symptoms.

Making a virtually “mite-free” house means identifying and eliminating any places where mites could lurk and grow. In addition to the strict measures applied to your bedroom, attention needs to be paid to the rest of the house, particularly to floors and carpets, soft furnishings, cushions and curtains.

• Replace fitted (wall-to-wall) carpets and rugs with vinyl or parquet flooring; you will eliminate an important allergen reservoir and it will be also easier to keep clean.
• Reduce the number of “dust collectors”: intricate or bulky decorations, heavy drapes, double curtains, tapestries, cushions, thick rugs, woolly throws, animal skins etc.
• Use a vacuum cleaner, fitted with a HEPA filter, frequently throughout the house. (vacuuming, even with the most efficient machines, stirs the dust up in the air and it will take a few hours for it to settle down again. It is therefore recommended that mite allergy sufferers should be out of the house for at least two hours when the cleaning is done).