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CASTOR OIL PHOSPHATE.

Valuable / ANTICAKING, EMULSION STABILISING

A high-performance phosphoric acid ester derived from castor oil that serves as a multifunctional anionic emulsifier and skin-conditioning agent. It is specifically engineered to stabilize complex formulations while providing a unique 'refatting' effect that protects the skin's lipid barrier.

Emulsion Stabilizing Anionic Surfactant Moisturizing Agent Pigment Dispersant Refatting Agent

Science

It functions by forming delicate hydrogen bonds with the skin surface, creating a protective film that prevents the stripping of natural epidermal lipids. As an anionic surfactant, it reduces surface tension and improves the wetting and dispersion of inorganic pigments like Titanium Dioxide and Zinc Oxide, ensuring uniform application in sunscreens and color cosmetics.


Research

Medium confidence
Effective range 1–25%
Optimal

5%

Key findings

  1. 01 Clinical observations in atopic dermatitis and psoriasis formulations indicate that phosphate ester surfactants reduce lipid extraction and improve barrier integrity compared to standard surfactants.
  2. 02 Technical evaluations demonstrate significant skin protection and moisturizing benefits when used as a co-emulsifier at concentrations between 5% and 20%.

Transparency

Not commonly dusted
Min. effective
1%
Red flag below
0.5%

As a functional emulsifier and stabilizer, it is typically used at 1% or higher to achieve formulation stability. Levels below this may indicate its use for label claims rather than structural or therapeutic efficacy.


The Formula

Solubility
Both
Optimal pH 3.5 – 9
0 7 14

Stability

Exhibits exceptional thermal and chemical stability across a wide pH range. It is suitable for both acidic and alkaline environments and can function as a secondary water-in-oil (W/O) emulsifier.

Synergies

  • Inorganic pigments (TiO2, ZnO)
  • Non-ionic surfactants
  • Roflumilast

Conflicts

  • Cationic surfactants
  • Strong oxidizing agents

Safety

CIR Status
Safe as used
Max tested
8.3%
Pregnancy
Safe
Sensitization risk Low

The CIR Expert Panel considers this ingredient safe when formulated to be non-irritating. The 8.3% benchmark is based on the highest concentration of related alkyl phosphates in leave-on products.


Your Skin

Yes Normal
Yes Dry
Yes Oily
Yes Sensitive
Irritancy Low
Comedogenicity Unknown

Our Assessment

Valuable

A sophisticated stabilizer and barrier-reinforcer that excels in high-pigment or medicated topical formulations where skin protection is paramount.


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References