Remove the mattress pad from the bed.
Read the mattress pad tag for the washing machine water temperature. If there is no tag, put the washing machine on cold since that is the safest temperature.
Fill the washing machine with water. Add a cup of bleach. Put the pad in the washing machine. Do not run the washing machine until the pad soaks for about 30 minutes.
Run the washer on a normal cycle. Remove the mattress pad and place it in the sun. Do not dry the mattress pad in a dryer because the heat may damage it.