If your sleeping bag is darkened with grime or worse yet—losing its loft—then it’s time to give it a good washing. Even if it doesn’t look less lofty, the buildup of body oils and dirt over time will migrate into the fill (both down and synthetic) and begin to compromise your bag’s loft and warmth.
You don’t want to wash your bag obsessively (after every trip), but laundering it yearly is a good idea. You can wash it in a bathtub (very labour-intensive) or send it to a professional cleaner. Or you can DIY that sleeping-bag cleaning job using a commercial-size washer and dryer (at a laundromat).
Because the interior lining at your bag’s head and foot areas tends to get extra dirty, you should consider spot cleaning those areas prior to washing the entire bag. (And sometimes all your bag needs is a little TLC, not a full-blown bath.) The spot cleaning process is simple:
Tip: Hold the shell or liner fabric away from the insulation so that you can wash and rinse the outer shell without getting the inner fill wet. If the fill does get wet, then give it plenty of time to dry before storing your bag.