What it is
Isostearyl isostearate is the ester of isostearyl alcohol and isostearic acid, both branched (iso) fatty chains. The branching keeps it liquid and gives a smooth, non-tacky, moisturizing feel while still being substantive on the skin. It is commonly used to wet and disperse mineral pigments and inorganic UV filters such as zinc oxide and titanium dioxide, which improves uniformity and reduces a chalky finish in mineral sunscreens and tinted products.
Safety & warnings
It is regarded as a mild, well-tolerated emollient. Because it is a heavier fatty ester, it can contribute to a rich, occlusive feel that some users prone to congestion may prefer to avoid in high amounts, though branched esters are generally less likely to clog pores than their straight-chain counterparts.
Origin & sourcing
Synthetic. It is made by esterifying isostearyl alcohol with isostearic acid, fatty raw materials that can be derived from plant or petrochemical sources.
Questions everyone asks
Why is isostearyl isostearate used in mineral sunscreens?
It helps wet and evenly disperse mineral UV filters and pigments, which improves spreadability and reduces a chalky or uneven finish.
Does isostearyl isostearate moisturize skin?
Yes, as an emollient it softens skin and leaves a smooth, cushiony feel, though it is a texture and conditioning agent rather than an active treatment.