STEARETH-21
Steareth-21 is a long-chain PEG ether: it combines an octadecyl chain, related to the fatty portion of stearyl alcohol, with ethylene oxide units. This arrangement gives it one part that associates with oily materials and another that interacts with water, a useful feature for building cosmetic emulsions.
STEARETH-21: what it is
Steareth-21 is a long-chain PEG ether: it combines an octadecyl chain, related to the fatty portion of stearyl alcohol, with ethylene oxide units. This arrangement gives it one part that associates with oily materials and another that interacts with water, a useful feature for building cosmetic emulsions.
The number 21 distinguishes Steareth-21 from names such as Steareth-2 and indicates a higher average degree of ethoxylation. Because it is a mixture of molecules of nearby sizes, it is not the same as pure stearyl alcohol: it is made to help water and oil phases stay dispersed rather than to act as a plant oil on the skin.
STEARETH-21: what it does in cosmetics
In lotions and creams, Steareth-21 helps keep water and oils together in a stable emulsion. In everyday use, that can help the product resist separating and spread more evenly. Its surfactant action can also take part in lifting oil and residue when it is included in a cleansing product.
One laboratory study tested a complete emulsion containing Steareth-21 together with Steareth-2 and cetearyl alcohol, measuring how sunscreen filters passed through human skin outside the body. That result describes the whole emulsifying system, not a benefit from Steareth-21 alone, so it does not support promises of sun protection, moisturising, or skin treatment.
Products containing this ingredient
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