Is Steareth-21 fungal acne safe?
Steareth-21 is generally considered safe for fungal-acne-prone skin. Stearyl alcohol (C18) ethoxylate with 21 EO units; in vitro Brij 721 was NOT assimilated by M. furfur (Dobler/Schwartz et al. Cosmetics 2019). Moved to safe 1 in tandem with Ceteareth-20 - same biology, same in-vitro evidence, same logic.
Also known as PEG-21 Stearyl Ether, Polyoxyethylene (21) stearyl ether, Brij 721, Brij S 21
Why this verdict
Stearyl alcohol (C18) ethoxylate with 21 EO units; in vitro Brij 721 was NOT assimilated by M. furfur (Dobler/Schwartz et al. Cosmetics 2019). Moved to safe 1 in tandem with Ceteareth-20 - same biology, same in-vitro evidence, same logic.
Fungal acne, properly called malassezia folliculitis, is driven by a yeast that feeds on fatty acids in roughly the C11 to C24 range. An ingredient is a concern when it can supply usable fatty acids in that window, and it is generally fine when it cannot. Chain length and ethoxylation can both change the verdict, which is why the chemical family alone does not decide it. See the full trigger list and how we assess ingredients for the reasoning and sources.
Frequently asked questions
Is Steareth-21 safe for fungal acne?
Steareth-21 is generally considered safe for fungal-acne-prone skin. Stearyl alcohol (C18) ethoxylate with 21 EO units; in vitro Brij 721 was NOT assimilated by M. furfur (Dobler/Schwartz et al. Cosmetics 2019). Moved to safe 1 in tandem with Ceteareth-20 - same biology, same in-vitro evidence, same logic. This is informational only and not a diagnosis; suitability varies by person and formulation.
Why is Steareth-21 considered fungal-acne safe?
Stearyl alcohol (C18) ethoxylate with 21 EO units; in vitro Brij 721 was NOT assimilated by M. furfur (Dobler/Schwartz et al. Cosmetics 2019). Moved to safe 1 in tandem with Ceteareth-20 - same biology, same in-vitro evidence, same logic. Fungal acne (malassezia folliculitis) is driven by ingredients that supply fatty acids in roughly the C11 to C24 range that the yeast can metabolize; Steareth-21 is assessed against that mechanism.
Assessed using: Simple Skincare Science (Brij 721 not assimilated), Dobler et al. 2019 MDPI Cosmetics, INCIDecoder.
This page is informational only and is not medical advice or a diagnosis. Fungal acne can resemble other skin conditions, and ingredient suitability varies by person and by formulation. Verdicts reflect community-reported data and malassezia lipid research, not a guarantee for your skin. Always patch test and consult a qualified clinician.