STEARETH-21 is a surfactant ingredient used in skincare formulations.
emulsifier
⚠️ Data is provided for informational purposes only. It may contain inaccuracies and should be independently verified. This is not medical advice. Consult a healthcare professional before making health decisions.
📋 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
No data yet
Not rated for this ingredient yet.
🛡️ Safety rating
Safety: Generally Low ConcernResearch confidence: Fair
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
EU: No restriction on fileUS: No restriction on file
💧 Skin Type Compatibility
No data yet
Per-skin-type data isn’t curated for this ingredient yet.
⚠️ Don’t Combine With
No data yet
No known incompatibilities on file for this ingredient.
📚 Research & Evidence
PUBMED CITATIONS
1
Data sources: EU CosIngPubMed
🔬 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.
