What it is
Steareth-21 is stearyl alcohol reacted with an average of about 21 ethylene oxide units, giving it a balance of oil- and water-loving character. It is commonly combined with the more lipophilic Steareth-2 to form a versatile emulsifier pair that stabilizes oil-in-water lotions and creams. In sunscreen formulas it helps build a uniform base that carries emollients and UV filters.
Safety & warnings
Steareth-21 is generally well tolerated and is not a common sensitizer. Like other PEG-type ethoxylated ingredients, it may carry trace 1,4-dioxane from manufacturing, which suppliers minimize through purification. It is not considered notably comedogenic at typical use levels.
Origin & sourcing
Synthetic. Made by ethoxylating stearyl alcohol, a fatty alcohol derived from plant or petrochemical sources.
Questions everyone asks
What is Steareth-21 used for?
It is a nonionic emulsifier that helps oil and water blend into a stable cream or lotion, often working alongside a lower-ethoxylated steareth.
Is Steareth-21 the same as Steareth-2?
No. Both come from stearyl alcohol, but Steareth-21 is far more ethoxylated and water-loving, so they are often paired to balance an emulsion.