Experts now recommend that your duvet and pillows are cleaned at least twice a year. It is a known fact that a typical duvet/Mattress Topper contains up to 20,000 live house dust mites along with bacterial and fungal spores they leave behind. Duvet/Mattress Topper cleaning provides highly effective sterilisation and removal of allergens, leaving your duvet fresh and hygienically clean.Duvet & Mattress Toppers.