Duvets & pillows should always be washed according to the detailed instructions on the care label.  

I have selected pillows for i love my that have excellent washability.  The fillings are made from polyester ball fibre that re-plumps after washing.  For allergy sufferers choose the spundown range which may be washed at 60^oC, the temperature which kills dustmites.  This pillow may be washed safely 25 times!

Natural pillows, with 100% cotton covers, may be washed and tumble dried.  Put three (clean) tennis balls in the machine with the pillow to ensure the filling is agitated during washing and drying.  Make sure the filling is completely dry before use.  Check the care label for detailed instructions.
Duvets and pillows must never be dry cleaned.  The solvents used would remain in the filling.  However your cleaner should offer a laundering service.