Fabric softeners coat the surface of a fabric with chemical compounds that are electrically charged, causing threads to “stand up” from the surface so the fabric feels softer and makes it fluffier. Cationic softeners bind by electrostatic attraction to the negatively charged groups on the surface of the fibers and neutralize their charge. The long aliphatic chains then line up towards the outside of the fiber, imparting lubricity.
Electrically conductive fabric softener chemicals may also prevent static charge buildup in clothes dryers. Other functions manufacturers claim include less friction during ironing, increased stain resistance, reduced wrinkling and pilling, and lower drying time. Most contain fragrances. Cationic fabric softeners are added during the rinse cycle rather than the wash cycle because they can interfere with detergent cleaning action.[citation needed] In addition to fabric softening chemicals, fabric softeners may include acids or bases to maintain optimal pH for absorption, silicone-based anti-foaming agents, emulsion stabilizers, fragrances, and colors.
As above, they also contain preservatives (CIT/MIT, BIT commonly) which some people are sensitive to (but many others are not) but they’re cheap and effective. Actually, many of the older sensitization reports are not as reliable as some manufacturers material were worse than others due to impurities as much as the CITMIT itself, but to an extent mud thrown has stuck.
And as above as well, don’t use them on technical fabrics or surfaces that are supposed to be absorbent, the lipophilic chains of the cationic surfactants will repel water / screw up the wicking properties.
