What is it?
An ester of stearic acid, a common fatty acid, and 2-ethylhexyl alcohol, a branched eight-carbon alcohol. It is an emollient: it softens skin and helps products spread smoothly, and it is used in lip products, eye makeup and skin care. Its older name is octyl stearate.
Key information
- The CIR Expert Panel has found it safe as used since 1985, and since 2013 on condition that products are formulated to be non-irritating.
- In 2013 it was reported in 335 cosmetic products, at up to 38 percent in eye-area products.
- Products with 25.9 and 38.8 percent did not cause allergic sensitization in repeat patch tests on volunteers.
- Despite the old name octyl stearate, it is not related to the sunscreen filter octinoxate (octyl methoxycinnamate).
More information
Ethylhexyl stearate is made by esterifying stearic acid with 2-ethylhexyl (“octyl”) alcohol. The product is then refined by catalyst neutralization, vacuum distillation or decolorizing and deodorizing steps that remove traces of alcohol.
The Cosmetic Ingredient Review (CIR) Expert Panel found it safe as used in 1985 and reaffirmed that in 2005. In 2013 it was one of 237 alkyl esters the panel concluded are safe in present practices of use and concentration when formulated to be non-irritating, a proviso it added because some esters in the group can irritate skin. At that time ethylhexyl stearate was reported in 335 products, at up to 38 percent. Undiluted, it was at most mildly irritating to rabbit skin. A formula with 7.6 percent was neither irritating nor sensitizing in 56 volunteers, and a lip gloss with 25.9 percent and an eyebrow pencil with 38.8 percent did not cause allergic reactions in repeat patch tests.
When the ester is broken down, it releases 2-ethylhexanol. The panel considered a reproductive toxicity finding linked to 2-ethylhexanol and concluded that, given how much would be absorbed and reach the liver, it was not an issue. It also noted that alkyl esters can help other ingredients pass through the skin, a point for formulators.
On pore clogging, its close relative ethylhexyl palmitate scored 4 of 5 in a 1989 rabbit-ear survey whose author called the model extremely sensitive; we did not find a score for ethylhexyl stearate itself in that survey. The old name octyl stearate can be confused with octyl methoxycinnamate, a sunscreen filter we rate Red Light, but the two are unrelated.
Sources: Cosmetic Ingredient Review: Amended safety assessment of alkyl esters as used in cosmetics (2013); Cosmetic Ingredient Review: Quick reference table of safety conclusions (September 2022); Journal of the Society of Cosmetic Chemists (1989): Comedogenicity and irritancy of commonly used ingredients in skin care products
