Fatty acid used as an emollient and emulsifier. It has been shown to protect skin's surface against water loss and help shore up skin's protective barrier. Stearic acid may be synthetic or animal-derived.
References for this information:
International Journal of Cosmetic Science, August 2013, pages 337-345
International Journal of Toxicology, Volume 24, 2005, Supplement 3, pages 65-74
International Journal of Pharmaceutics, February 2000, pages 189-195