Hydroxystearic Acid at a Glance
- May be derived from castor oil or created in a lab
- Also known as octadecanoic acid and 12-hydroxystearic acid
- Considered a surfactant when used in soaps
- Considered a hydrating fatty acid when used in leave-on products
Hydroxystearic Acid Description
Hydroxystearic acid is a fatty acid-based ingredient that has much versatility. It can work in cleansing formulas as a surfactant while adding emollient and texture-enhancing properties to products such as moisturisers, makeup, and sunscreens.
The natural form derived from castor oil is used most, but hydroxystearic acid can also be made synthetically. It is chemically similar to stearic acid, another fatty acid used in thousands of skin care, makeup, and hair care products since it is non-irritating and works well in many types of formulas.
Emerging research from a supplier of an oleic acid-derived form of hydroxystearic acid shows it may play a role in reducing pore size and fading discolourations; however, independent research is needed to verify such claims.
Research from Unilever shows it works to help offset hyperpigmentation triggered by exposure to airborne pollutants, possibly due to its antioxidant ability which prevented the oxidation of lipids (fats) in skin that would normally occur when exposed to such pollutants.
Hydroxystearic acid is considered safe as used in cosmetics at concentrations of 10% or less. The typical usage level for this ingredient is 1–5%.
Hydroxystearic Acid References
International Journal of Cosmetic Science, June 2019, pages 240–256
Experimental Dermatology, June 2019, pages 742–746
International Journal of Toxicology, Volume 18, Issue 1, January 1999, pages 1–10
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About the Experts
Paula Begoun is the best-selling author of 20 books about skincare and makeup. She is known worldwide as The Cosmetics Cop and creator of Paula’s Choice Skincare. Paula’s expertise has led to hundreds of appearances on national and international radio, print, and television including:
The Paula's Choice Research Team is dedicated to busting beauty myths and providing expert advice that solves your skincare frustrations so you can have the best skin of your life!