Real Simple answers your questions.
Q. How do I wash my down-alternative comforter without taking it to the dry cleaner?
A. Most down-alternative comforters are machine washable, but it’s best to do this in a large commercial machine at the neighborhood Laundromat. A smaller household washer could compress and distort the filler, says Allen Rathey, president of housekeepingchannel.com.
Wash the comforter with the machine set on the gentle or delicate cycle, using cool or warm water. Since every comforter is a bit different, check the care tag or contact the manufacturer for detergent suggestions. Then dry the comforter on low heat with a few tennis balls to plump it up. Or consider using Down Fluffer rings ($15 for 2, thecompanystore.com), which help, you guessed it, fluff your comforter in the dryer.
Keep your comforter clean in between washings by protecting it with a duvet cover. When the cover needs a cleaning, it will easily fit, just like bed linens, into a household washing machine. ―Sharon Tanenbaum