Fill a sink with warm water and add a bit of mild detergent.
Submerge the unzipped pillow and knead it in the soapy water until any stains or dirt have been washed away.
Rinse the pillow thoroughly and wring out all excess water.
Place the pillow in the sun to dry or hang it on a drying rack.
Add a small amount of gentle detergent to your washing machine and set it on its most delicate mode. If your machine has a "hand wash" cycle, select this mode.
Add a few towels to balance the load and start the wash cycle.
Place the pillow in the sun to dry or hang it on a drying rack, after washing is completed.