Good point Francies41. dryer sheets do cause a build up in the dryer, Fabric softeners cause a build up in your washer. If you are washing polar fleece do not use either one and do not use liquid laundry detergent. Those products cause the polar fleece to become stiff over time and reduce the amount of wind resistance in the fleece. I use the dryer balls from Norwex. I think they work well for me.