Bedroom

The areas of highest concentration of mites and mite antigens within the bedroom are often the sleeping area, this includes the mattress and bedding (Sidenius et al. 2002). This is due to the favourable conditions in the bed. Skin flakes and other dander found in the bed are replenished every night when the bed is used by its owner.

Washing bedding above 40°C reduces allergen concentrations of carpets as well as of beddings. Washing at 40°C does not affect the allergen concentrations in the mattress and does not seem to destroy the mites (Arlian et al. 2003; Luczynska et al. 1998). In Ohio, 13 houses were examined for the presence of mites on different parts of the bed (Yoshikawa and Bennett 1979). The majority of mites were recorded from the mattress, followed by the blanket and the pillows. The mattress edge harboured the highest concentrations when compared with the head sites of the bed.

Foam mattresses can be four times more likely to contain mites than sprung mattresses (Schei et al. 2002). Traditional sprung mattresses had a thicker covering which is more impermeable to mites than the thinner covering on foam mattresses.

Other areas in the bedroom in which mites thrive are textiles such as the curtains and the carpet. The concentration of mites in bedding affects concentrations of mites in these textiles, as the concentrations of allergens in the carpet are related to the age of the bedding (Luczynska et al. 1998). Curtains are an area of the house that often includes other interesting mite species. Binotti et al. found phytophagous Eriophyidae (Prostigmata) and ground mites of the order Oribatida in curtains in Brazil (Binotti et al. 2005). The authors suggest that wind may have a large part to play in the mite contamination of curtains. However, the association of Oribatida with curtains is not surprising. Phauloppia lucorum, the window sill mite, aggregates in large numbers around windows inside houses. Although this species is associated with different habitats outdoors, such as lichens, indoors it has its specific distribution (Hughes 1976).

Stored product mites are also common inhabitants of our bedrooms, they are found in association with fungi that grow here. Mould from residual damp on the walls or fungi that are found in the bed can be a source of food for stored product mites. The fungi or molds are often not obvious to the naked eye. In the tropics, stored product mites can become the most abundant mite in the bedroom. A study in Singapore found that Blomia tropicalis (Glycyphagidae, Astigmata) was the most abundant mite in the bedroom, whereas in temperate climates, it is usually thought to be Dermatophagoides pteronyssinus (Chew et al., 1999a, b). This may be due to the warm and humid nature of the tropics encouraging fungal growth, changing the constituents of the dander in the bedroom in comparison to temperate climates. This would favour stored product mites over house dust mites.

Predatory mites such as species within the Cheyletidae (Prostigmata) are found in homes. They are found in association with the mites on which they feed. If we assume that the bedroom contains the highest numbers of mites, it may be safe to propose that they also contain the highest concentration of predatory mites. Warner et al. found Cheyletidae mites in 22% of homes in a study in Sweden (Warner et al. 1999). Chew et al. (1999a, b) found that homes with predatory mites contained relatively few Astigmata mites, which are stored product and house dust mites, suggesting they play a part in balancing the ecosystem in our homes.

Concrete floors in the bedroom are thought to increase humidity, corresponding to higher allergen level in mattresses. The level in a house, on which bedrooms are found also affect concentrations of allergens. Luczynska et al. (1998) showed that having a bedroom on the ground floor greatly increased concentrations of allergens. This may be due to increased humidity or reduced ventilation.

Mites can be found in great numbers on clothing. Bischoff et al. (1998) propose that between 20,000 and 30,000 house dust mites can be found in various items of clothing. They also showed that washing at low temperatures only removes around 70% of the population, leaving some to carry on the next generation. All this implies that mite numbers in a large wardrobe could make millions.

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