Common Name(s): Polyhydroxystearic acid,phsa,12-hydroxystearic acid polymer
DESCRIPTION
What It Does: Helps create stable w/o emulsions and keeps mineral sunscreen ingredients evenly dispersed.
Why It's Used: Phsa is specifically valuable in sunscreen formulations for stabilizing mineral sunscreens (tio2/zno) in w/o emulsions and for dispersing mineral pigments in color cosmetics.
How It Works: Polymerized 12-hydroxystearic acid forms a coiled polymer structure that adsorbs onto mineral particle surfaces; stabilizes pigment/sunscreen dispersions by steric exclusion; enables stable w/o emulsions with mineral uv filters.
Typically Found In: Mineral sunscreens,color cosmetics,w/o emulsions,pigment dispersions
TECHNICAL DETAILS
Primary Category: Functional ingredient โ emulsifier
Secondary Functions: Dispersing agent,pigment dispersing,w/o emulsification
Application Areas:
Facial Skincare
Body Care
Hair Care
Beard Care
Color Cosmetics (Makeup)
Dietary/Oral Supplements
Typical Concentration Range: 0.5%โ5%
SOURCING & ETHICS
Vegan Status: Conditional - feedstock declaration required
Halal Status: Unverified - feedstock declaration required (plant, animal and petrochemical routes all exist)
Source Notes: Polymerized 12-hydroxystearic acid from hydrogenated castor oil (ricinus communis); naturally derived. [audit 2026-07-29 rev2: origin-dependent: the same inci exists in plant, animal and petrochemical versions and the name does not discriminate. determination requires shariah-panel sign-off.]
SKIN COMPATIBILITY
Irritancy Rating: 1/5 โ very low
Comedogenicity Rating: 1/5 โ low
Sensitivity Concerns: Generally well tolerated. used extensively in sunscreen formulation.
Safe for Sensitive Skin: Yes
SAFETY & COMPATIBILITY
Safety Profile: Excellent safety profile. ewg score: 1.
Works Well With: Hydrogenated castor oil derivatives,mineral sunscreens (tio2/zno),mineral pigments,w/o emulsifiers
Avoid Combining With: Not compatible with highly aqueous systems (lipophilic polymer)
SCIENTIFIC NOTE
Polyhydroxystearic acid (phsa) is a specialty polymer emulsifier derived from ricinoleic acid polymerization; it adsorbs onto mineral particle surfaces via the terminal carboxylic acid, with the polymer chains providing steric stabilization of the particle dispersion.
Last Verified: 2026-03-27
Primary Sources: Cosing database,inci dictionary,croda hypermer sunscreen technology,european sunscreen association