How you clean a comforter depends on the material used in the cover and filling. Most can be washed in cold water in the washing machine, and dried outside (except kapok and viscose from bamboo, which need to be fluffed in a dryer), or tumbled dried on low. Be sure to read the manufacturer's recommendations for the comforter you choose. If you keep a cover over your comforter, you can wash that more frequently and cut down on how often you need to wash the comforter itself—if you don’t sweat at night, you might not need to clean your comforter more than once a year. Hanging a comforter outside in the sunshine every few months can also help keep it fresh-smelling and fluffy.