Most British single men ages 18-25 change their sheets four times a year, a survey indicates.Ergoflex UK, a maker of memory foam mattresses, which conducted the survey, said 55 percent of the younger men changed their sheets on average every 3.1 months, although 17 percent of single men admitted a prospective romantic partner was turned off by a dirty bed. On the opposite of the cleanliness scale -- 62 percent of women ages 35-50 changed their sheets on average every week. However, once men were in a relationship, 8-in-10 women took over bed changing duties and they changed sheets an average every 2.3 weeks. Steven Willis of Ergoflex said dust mites are a tiny parasite that lives on human skin cells and other organic waste. They can be found in various places in the home, but they prefer warm, dark environments with a regular supply of food such as beds. High concentrations of dust mite allergens are a risk factor for allergies and related diseases such as asthma and hay fever. Washing bed linens once a week in hot water -- water temperature of 130 degrees F or higher -- will kill dust mites. Bed bugs, which can live in the interior cavities of certain types of mattresses and bed bases, can bite those who share the bed with them. To prevent bed bugs wash sheet and all bedding materials and dry using the \"hot\" setting. Vacuum all the surfaces of a home -- walls, floors and furniture. No survey details were provided.