Once or twice a year, take your natural duvet to the cleaners and they will launder and dry it for you.  Professional cleaners have huge drying machines to ensure your duvet is fully dry and won’t develop mildew.

Synthetic duvets may be washed.  Depending on the size of your washing machine most single synthetic duvets may be washed at home – check the care label to see the recommended temperature.  For doubles, king size and superking it’s best to take your duvet to the cleaners – or even better choose the spundown duvet – all sizes fit into a domestic washing machine – it can be washed at 60^oC the temperature that kills dustmites.
Remember duvets and pillows must not be dry cleaned – a professional cleaner will launder them for you.
In between washes shake your duvet daily and when you make your bed fold it back, away from the bottom sheet to allow your duvet to air.  You may even hang your duvet outside to freshen it up.