A fabric softener (American English) or fabric conditioner (British English) is a conditioner applied to laundry after it has been washed in a washing machine. A similar, more dilute preparation meant to be applied to dry fabric is known as a wrinkle releaser.
Fabric softeners reduce the harsh feel of items dried in open air, add fragrance to laundry, and/or impart anti-static properties to textiles. In contrast to laundry detergents, fabric softeners are considered a type of after-treatment laundry aid.[1]
Fabric softeners are available either in the form of a liquid, typically added during the washing machine's rinse cycle, or as dryer sheets that are added to a tumble dryer before drying begins.[1][2] Liquid fabric softeners may be added manually during the rinse cycle, automatically if the machine has a dispenser designed for this purpose, through the use of a dispensing ball, or poured onto a piece of laundry to be dried (such as a washcloth) which is then placed into the dryer.
Washing machines exert significant mechanical stress on textiles, particularly natural fibers such as cotton and wool. The fibers at the fabric's surface become squashed and frayed, and this condition hardens into place when drying the laundry in open air, giving the textiles a harsh feel. Using a tumble dryer results in a softening effect, but it is less than what can be achieved through the use of a fabric softener.[3][1]
As of 2009, nearly 80% of households in the United States had a mechanical clothes dryer.[4] Consequently, fabric softeners are primarily used there to impart anti-static properties and fragrance to laundry.