Why ventilate your home against house dust mites?

Scientists have repeatedly found that the reduction of indoor humidity through the use of ventilation systems is associated with lower exposure to dust mites and allergens. They have also shown that HDM droppings can remain intact for several months at room temperature. (1,2)

Without ventilation the droppings, released by activity, are free to roll around on smooth flooring or become part of a dust-bunny, or 'snagged' in carpets or cloth. Good, appropriate ventilation (e.g. by opening windows, using extractor fans in the bathroom and kitchen) can reduce humidity, reduce the risk from molds and contact with HDM droppings, a known risk factor for allergic sensitization. (3)

Warning: Held within a dropping are several enzymes designed to either breakdown left over food or protect the mite from infection. Of all the enzymes there is one that is like a powerful meat tenderiser used in the food industry. The food tenderiser is 'papain', the mites's enzyme/allergen is named Der p1, and is a major cause of sensitisation (irritation), or allergy around the world. Once released from the dropping Der p1 goes to work to breakdown the 'glue' that holds defence cells together in the lung, nose or on skin. The temporary breach allows opportunistic bystanders access to the body. Avoidance of HDM contact is the first step in the management of HDM related disease. (4,5,6)

In clinical studies central heating was both negatively and positively associated with house dust mite concentrations. This may be due in part to patterns of use in different parts of the world, as well as comparisons of central heating with different types of heating. Centrally heated homes may be less ventilated because there is a tendency to keep windows closed if the heating is on. In one study the presence of open fireplaces in the living room was associated with a lower concentration of Der p1. The fireplaces usually were not used, they represented a ventilation factor rather than a heating factor. (7)

How ventilation becomes the essential part of a healthy indoor environment is the choice of homeowners, schools and employers. There is a wide range of expert advice available, including (weather permitting) opening windows to send harmful dust outdoors where it won't threaten or harm the vulnerable. The purpose of ventilation.