Down comforters should be fluffed frequently, preferably every day. They should also be covered with a duvet to protect from spills. If adequately protected, they do not require frequent cleaning. In fact, many down comforter manufacturers recommend that down comforters only be cleaned every few years, though they should be aired out occasionally.
When washing down comforters is necessary, it is best to leave it to a professional cleaner. While down can be dry-cleaned, the results are better if it is instead cleaned with specially designed solutions.
If, however, you prefer to do it yourself, you will need to use an oversized front-loading commercial grade machine. If needed, you can use non-chlorine bleach. Do not use your home machine. It is not designed for cleaning large down comforters. Using it could lead to damaging your comforter—or your machine.
After washing down comforters, you should dry them in a large commercial dryer on medium heat. Although this could take several hours, do not try to speed up the process by using high heat. This can burn the comforter. Even on medium heat, it is important to check periodically and make sure the unit is not overheating. Be patient during the long drying process -- failure to properly dry your down comforter could lead to mildew growth.
With proper care and infrequent washing and drying, your down comforter can provide many years of reliable warmth and comfort.