A few common sense sleeping bag care practices will keep your bedroll relatively clean and intact.
A down bag is of little value if the sack spews fluff every time you snuggle into it. Since a down-filled bag is one of the most delicate items of camping gear, it must be treated with respect if it's to give you years of use. I’ve compiled these sleeping bag care recommendations to help you have those years.
The nylon shell of a typical down bag is sturdy but thin, so it should be protected from wet weather and snags. When you camp outdoors, always place a waterproof layer (such as a groundsheet or foam pad) between the sack and the earth to prevent the bag from soaking up moisture or ripping on a stick. (If a snag does occur, don't be caught unprepared: always include a roll of ripstop tape in your hiking kit)
Be leery as well, of snuggling too close to the campfire. And if your bag gets wet, don't try to steam the dampness out. Down does take an inconveniently long time to dry, but if you move closer to the blaze to speed the process, you'll likely scorch the covering fabric and ruin your bag.
Besides keeping an eye on the outer surface, you'll want to give your sleeping bag's innards some attention. The warmth of down is a result of its lofting ability. Air trapped by the fluff provides insulation. Therefore, be sure to shake your bag out and place it under shelter immediately after making camp to allow the down to attain its maximum loft. (This rule holds true at home as well. Never store the snugsack in its small carrying bag, as this can cause the tiny feathers to break and mat together.)
It's also a good practice on the morning after the sleepout to let the bag air-dry before you pack it up. (If you're unable to dry the sack when you first get up, do take a moment later in the day to stop and shakeout the bedding. You'll thank yourself when you crawl into a dry, well-lofted down sleeper in the evening!)
By far the biggest controversy concerning sleeping bag care involves how best to clean the feather-filled sacks. Some enthusiasts vow that the sleepers should never be washed — and when the bag becomes too dirty for comfort, such folks just discard it!
Most hikers, however, agree that occasional washings won't damage the down. A simple water and soap solution is generally favored over dry cleaning, because chemical cleaning solvent tends to remove the natural oils from the down and leave a residue on the bag's surface. In addition, the cleaning fluid is extremely toxic and could be dangerous to campers who fail to air their bedding properly. So if you must dry clean your sleeping bag, be certain that the operator has had experience with down garments and uses a petroleum-based cleaning compound (as opposed to a chlorinated hydrocarbon solvent). Then air your bag completely for as much as a week before sleeping in it.
The majority of backpackers, though, prefer machine or hand washing to dry cleaning. Some use a mild soap, then carefully lay the sack out flat in the sun for several days to air-dry. (Never hang a wet sleeping bag on a line; the inside baffles that hold the down in place could rip out when stressed by the added weight of the water.)
Other hikers maintain that a quality bag won't be harmed by machine washing. If you agree, do be sure to use cool or lukewarm water and mild soap (not detergent). It's also a good idea to use a front-loading (tumble) machine rather than the agitator type, as the latter could tear the nylon shell. You can machine-dry the sacks at a low to medium heat setting as well. Throw a clean sneaker in the clothes dryer with the bag; the combination of rubber and nylon causes a buildup of static electricity and helps give loft to the sleeping sack, and the footgear will also help break up any clumps of down.