Down mattress toppers give new life to an old, uncomfortable mattress or to simply make your mattress more luxurious. Down requires more infrequent cleaning than other types of bedding fillers because too much cleaning can damage the down and shorten the overall life of the topper.
Bring your topper to a laundromat and wash it in a large-capacity washer. Use warm water and set the machine to the "Delicate" cycle.
Use a very mild detergent. Add slightly less than the recommended amount for one load.
Put the topper through two rinse cycles, if possible. If that isn't possible, make sure the topper is completely rinsed before drying it. Use less than the recommended amount of detergent to ensure that it rinses well.
Dry the topper on a low setting in a tumble dryer.
Hang the topper to air dry for 8 to 12 hours after it comes out of the dryer, just to be sure the down is thoroughly dry.