STEARETH-21

📋 Quick facts

Description: STEARETH-21 — emulsifier.

All Functions: emulsifier

Quick Facts:

• Category: surfactant

Proven Benefits At A Glance:

• Steareth-21 is an emulsifier used in oil-in-water skincare formulations
• In one study, it was part of an emulsifier system that reduced how much of certain sunscreen ingredients passed through human skin in lab testing
• The choice of emulsifier in a product can significantly affect how ingredients penetrate the skin

📊 Comedogenicity

🛡️ Safety rating

Safety tier is a starting heuristic from regulatory status and comedogenic rating, not a dermatological verdict — see our Terms for the full disclaimer. Research confidence reflects how many real cited studies back this ingredient, not the strength of their findings.

🌍 Regulatory Status

💧 Skin Type Compatibility

⚠️ Don’t Combine With

📚 Research & Evidence

🔬 The Science

Steareth-21 is a type of emulsifier—a molecule that helps mix oil and water-based ingredients together in skincare products. In a 2008 study published in the International Journal of Cosmetic Science, researchers tested different emulsifier systems in sunscreen formulations to see how they affected whether active sunscreen ingredients could penetrate human skin. #1: When steareth-21 was used as part of an emulsifier system (combined with steareth-2 and cetearyl alcohol), it appeared to limit skin penetration of certain sunscreen agents. Specifically, for one sunscreen ingredient tested (butylmethoxydibenzoylmethane), the formulation containing steareth-21 allowed significantly lower amounts to pass through human skin compared to several other emulsifier systems tested (Int J Cosmet Sci, 2008).

For a different sunscreen ingredient (octylmethoxycinnamate), the steareth-21-containing formulation also ranked among those with the lowest skin penetration, though the effect was less dramatic than for the other ingredient. It’s important to note that this was a single laboratory study using human skin samples in controlled conditions—not a study on living skin. The researchers emphasized that emulsifier choice matters significantly when formulating sunscreen products, and vehicle (the base formula) effects should be carefully considered. However, the sources provided don’t explain *why* steareth-21 has these effects, nor do they provide information about other potential benefits or concerns with this ingredient.

📄 Related Research

Matched by search — not necessarily verified support for every statement above.

• Montenegro L et al. (2008). In vitro skin permeation of sunscreen agents from O/W emulsions. Int J Cosmet Sci.

🧴 Products Containing STEARETH-21

• SOOA SOOA Déobille à la pierre d’alun
• Henkel, Göt2b got2b kleber spiking wax
• Labell, intermarché Labell Déodorant Vanille des îles
• Nivea Men Dry Impact deodorant
• Nivea Dry Comfort
• Nivea Protect & Care
• BRYNILD GRUPPEN AS Nivea Roll-On Men Dry Fresh 50ml
• sanex zero%
• Babaria Desodorante rosa mosqueta
• Giorgi Fijación y textura
• Clairol Nice ‘n Easy Root Touch-Up Permanent Hair Color, 4R Dark Auburn
• BYPHASSE DEODORANT 48 H
• Barnängen, Schwarzkopf & Henkel Barnängen Active Pearls Aqua spirit
• Ducrem Emulsion reparadora y refrescante
• EuPhidra Sudorazione intensa
• Bonté Desodorante
• Borotalco Borotalco Invisible Deodorant Roller
• Axe AXE GEL CHEVEUX Extrême Look Pot 75ml
• Sanex Active Control
• Colgate-palmolive norge Palmolive Roll-On Happyful 50ml
• Palmolive Roll-On Soft floral
• COLGATE PALMOLIVE NORGE AS Palmolive Roll-On Anti-stress 50ml
• COLGATE PALMOLIVE NORGE AS Palmolive Roll-On Feel Glamorous 50ml
• Sanex Natur Protect
• Colgate-palmolive norge Palmolive Roll-On Sport 50ml
• Sanex Ph balance extra control
• Gold Bond Diabetics’ Dry Skin Relief Foot Cream
• Moisturiser
• Olay Regenerist Collagen Peptide 24 Cream Cleanser
• Vitamins and Sea beauty Sea Salt Coconut Face Scrub
• Amie naturally, spring clean Deep cleansing Mask
• OleHenriksen,Ole Henriksen Banana Bright+ Instant Glow Moisturizer
• OL, Olympique Lyonnais, Secret des Dames Lait corps riche et soyeux
• Veet Déodorant Crème 3
• henkel, schwarzkopf, taft Cire Wax Effet Sculptant Force 6
• Soft (carrefour) Dermo protection anti-transpirant
• Cosmia Anti-transpirant soft skin
• Cosmia Déodorant vanille
• Cosmia Anti-transpirant dry protect
• Guerlain L’institut Crème remodelante corps sublime