Wash the comforter with the machine set on the gentle or delicate setting with two rinse cycles, using cold water. Add a small amount of mild or all-natural detergent. Too much soap can strip the comforter, so be sparing. Dry the comforter in an extra-large capacity dryer on the lowest temperature setting possible. This will take 2-3 hours, but you want to make certain that the comforter is completely dry, to prevent mold growth.
Note: Wash your comforters once a year at most. To keep them clean in between washings