Take off all of the sheets and the mattress pad. Thoroughly vacuum the mattress using a vacuum attachment.
Sprinkle baking soda on top of the mattress. Sprinkle just enough so that the top of the mattress is dusted.
Allow the baking soda to settle into the mattress for five minutes. Vacuum the mattress once again to remove the baking soda. This will not only sanitize the mattress, but it will take away any bad smells or moisture.
Mix 1 cup of white vinegar and 1 cup of hydrogen peroxide into a spray bottle. Add 4 cups of cold water to the cleaning solution. Shake the spray bottle thoroughly to mix the chemicals. Lightly spray the mattress with the solution. This will sanitize the mattress completely.
Blot the cleaning solution using a dry towel. This needs to be done rather quickly because leaving the solution on can bleach the mattress. Allow several hours for the mattress to dry.