Science
Mechanism of Action
This ingredient forms a thin, imperceptible film on the skin's surface, acting as a protective barrier against environmental irritants, allergens, and bacteria, thereby preventing moisture loss, dryness, and itchiness. It reinforces the skin's natural lipid barrier, promoting enhanced hydration and resulting in a softer, smoother, and healthier-looking complexion. In sunscreens, it acts as a dispersant to uniformly coat inorganic oxide particles like titanium dioxide and zinc oxide, optimizing UV absorption and significantly reducing visible white cast. For color cosmetics, it ensures even pigment distribution, leading to a more consistent color payoff and improved wearability.
Research
Clinical Evidence
High confidenceN/A
Key findings
- 01 A Human Repeated Insult Patch Test (HRIPT) involving 51 subjects demonstrated that neat (100%) polyhydroxystearic acid was not irritating or sensitizing.
- 02 A modified Marzulli Maibach HRIPT, conducted on 107 subjects, confirmed that a product containing 3.45% polyhydroxystearic acid was neither irritating nor sensitizing.
Transparency
Dusting Analysis
The Formula
Formulation
Stability
Polyhydroxystearic acid is soluble in various oils, including castor oil, mineral oil, isododecane, isopropyl myristate, isononyl isononanoate, and pentaerythrityl tetraethylhexanoate. It remains insoluble in water, ethanol, propylene glycol, cyclopentasiloxane, or dimethicone. It typically presents as a soft, waxy solid or a viscous liquid at room temperature, with a melting point ranging from 50-70°C, ensuring broad compatibility with diverse resins, solvents, and additives in formulations.
Synergies
- Acts as an effective dispersant for inorganic UV filters (titanium dioxide, zinc oxide), enhancing their uniform distribution and reducing visible white cast in sunscreens.
- Compatible with a wide range of resins, solvents, and other additives, offering formulation flexibility.
Safety
Safety Profile
The Cosmetic Ingredient Review (CIR) Expert Panel has concluded that Polyhydroxystearic Acid is safe for use in cosmetics at current concentrations, with the highest reported concentration being 14.2% in lipsticks. It is not restricted for use in the European Union, is considered exempt from tolerance as a low-risk polymer by the FDA for pesticide formulations, and has been approved by the European Food Safety Authority (EFSA) for use in consumer food packaging, highlighting its robust safety profile across multiple industries.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Polyhydroxystearic acid is a valuable, multifunctional ingredient that significantly enhances product texture, stability, and wearability while offering low-risk emollience and barrier support suitable for all skin types.
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References
Sources