Fabric softeners are added to machine wash laundry. They soften the fabric by covering the textile fibers with a thin layer, this gives a soft feel and prevents stiffness. Fabric softeners are amid amines or imidazolines made from a fatty acid and an Ethyleneamine.
The fatty acids used often impart a rather strong smell which has to be masked by a perfume. Concentrations of 15% and higher of the ready for use fabric softener are now common practice. Also softergents – detergents with a softener incorporated into it – are on the market.