While you may have your own personal preferences about how frequently you change your bed's sheets, once a week is a general rule of thumb. The longer the sheets stay on the bed, assuming the bed is used on a daily basis, the more soiled they become -- coated with dust mites, perspiration and skin particles. Changing and washing the sheets on a weekly or at least biweekly basis helps keep the dust mites at bay, resulting in a cleaner room and better sleeping experience overall.
The Dirty Truth
Perspiration occurs as you rest in bed, whether you are aware of it or not. You may lose up to a liter of perspiration in a night, especially if the room is humid or if you sleep under lots of covers. Skin cells that you shed between the sheets are tasty treats for dust mites. Lint, makeup, bacteria and dust are also embedded in the sheets. If your pets are allowed in the room, pet fur and dander are most likely present as well. None of these pose health risks for healthy people, but if you suffer from asthma or allergies, all of this residue may trigger a reaction.