Fabric softeners reduce the harsh feel of items dried in open air, add fragrance to laundry, and/or impart anti-static properties to textiles.
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.
Some work better on cellulose-based fibers (i.e., cotton), others have higher affinity to hydrophobic materials like nylon, polyethylene terephthalate, polyacrylonitrile, etc.
[not specific enough to verify] Microemulsions provide the advantage of increased ability of smaller particles to penetrate into the fibers.
[6] Fabric softener reduces the absorbency of textiles, which adversely affects the function of towels and microfiber cloth.
[7][failed verification] Formerly, the active material of most softeners in Europe, the United States, and Japan, was distearyldimethylammonium chloride (DSDMAC) or related quat salts.
Anionic softeners and antistatic agents can be, for example, salts of monoesters and diesters of phosphoric acid and the fatty alcohols.
[9] Manufacturers produce some fabric softeners without dyes and perfumes to reduce the risk of skin irritation.
Some deaths have been attributed to this phenomenon,[10] and fabric softener makers recommend not using them on clothes labeled as flame-resistant.