Is
Isostearic Acid
Isostearic AcidBarrier
A branched fatty acid that stays liquid, softens skin and helps powders and oils hold together.
What it does
It’s a relative of stearic acid with a branched chain, which keeps it liquid at room temperature. It binds powders, helps oil and water blend, and adds a soft feel.
The evidence, graded
expert consensusUS safety reviewers (2019) assessed 102 fatty acids and their salts, which products use mostly to stop caking, steady mixtures or thicken. Behenic, arachidic and isostearic acid and magnesium stearate are in their conclusion. Behenic acid is used at up to 14% in lipstick, magnesium stearate at up to 7.2% in face powders. Some of these can irritate skin, and the less stable fatty acids can break down into compounds that cause allergy. So products must be made not to irritate or cause allergy.Burnett 2019 · Cosmetic Ingredient Review ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
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