Cationic surfactants are also added to detergent mixtures, and to laundry rinse water as fabric softeners. Usually a particular surfactant which is called an Esterquat, is used for this purpose. (www.scienceinthebox.com)
This means if you are adding fabric softener to your wash you are coating your laundry with a layer of rather large surfactant molecules. The problem with this, is that these molecules are not strongly bonded to the fabric that they are “softening” and are quite free to rub off onto your skin. Your skin will provide a rather attractive substrate for this type of molecule to adhere too. Given sufficient time, and quantity, a lot of this substance could end up right inside your skin cells.
Exactly the implication of this absorbent into the human body is not clear, but I would note that in a study on the toxic nature of a select group of anionic and nonionic surface active agents, one of the overall conclusions of the study was that the larger the molecular weight of the compound tested, the higher the toxicity levels observed in the results. The fabric softener Esterquat is definitely a larger molecule.