For any wet spills or stains, use a dull knife or spoon to lift away any solids from the surface. Next, use white paper towels to blot up as much moisture as possible. If the spill is large, remove the topper from the mattress to prevent soak through. Move it to a nonporous floor area (tile, vinyl, or sealed concrete) to clean.
Once you have removed as much moisture as possible, dampen the stain with clear water and sprinkle with laundry borax. Working from the outside edge of the stain toward the center, work the borax into the stain with a sponge or clean cloth until it is absorbed. Allow the borax to sit for at least 15 minutes. Then, use a handheld vacuum or the brush attachment on a standard vacuum to remove the residue. Repeat if necessary.
For blood stains, dampen a sponge or clean white cloth with two percent hydrogen peroxide. Blot the stain from the edges toward the center to prevent spreading. Keep moving to a clean area of the cloth as the stain is transferred. NOTE: Hydrogen peroxide may cause the foam to yellow and discolor but will remove the blood without crumbling the foam.
For tough odors from urine or vomit, clean the area then sprinkle the entire surface of the stain with baking soda. Allow the baking soda to sit on the mattress for 24 hours and then vacuum away. This will also help with cigarette smoke odors.
A commercial odor removal spray like Febreze or Ozium can also help refresh a foam topper.
After any stain removal process, allow the topper to air dry at least 24 hours before replacing it onto a mattress. If possible, stand the topper on its edge or elevate so there is air flow around all surfaces. Drying time may need to be extended if the stain removal was extensive.