You can put many wool or down mattress toppers in the washing machine, but memory and latex foam mattress toppers should be spot-cleaned to avoid shrinkage. To clean a foam mattress topper, dab stains with a towel, mix a vinegar solution in a spray bottle, spritz any stains, sprinkle baking soda onto the topper, wait for eight hours, and dry your topper with a handheld vacuum. Read your mattress topper’s label carefully to determine exact cleaning instructions.