Common Name(s): (z)-9-octadecenoic acid,cis-9-octadecenoic acid,elaidic acid (trans)

CAS Number: 112-80-1

DESCRIPTION

What It Does: Provides deep-penetrating emolliency and penetration enhancement for co-applied actives.

Why It's Used: Penetrating emollient and penetration enhancer for formulations requiring deep emolliency or enhanced active delivery.

How It Works: Cis double bond at c9 creates a 'kink' in the chain disrupting close packing, providing liquid phase at room temperature. this molecular kink also disrupts stratum corneum lipid packing for penetration enhancement. rapid skin penetration provides 'sinking in' emolliency.

Typically Found In: Facial oils,deep penetration products,penetration-enhanced formulas

TECHNICAL DETAILS

Primary Category: Functional ingredient – c18:1 omega-9 fatty acid

Secondary Functions: Barrier sealing,softening

Application Areas:

Typical Concentration Range: 1%–30%

SOURCING & ETHICS

Vegan Status: Conditional - feedstock declaration required

Halal Status: Unverified - feedstock declaration required (plant, animal and petrochemical routes all exist)

Source Notes: Plant-derived, synthetic or animal-derived. verify source. [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 – very low

Comedogenicity Rating: 2/5 – low to moderate (penetrates comedone-prone follicles)

Sensitivity Concerns: Non-irritating.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Excellent safety profile. ewg score: 1.

Works Well With: Humectants,ceramides,actives as carrier

Avoid Combining With: No significant incompatibilities

SCIENTIFIC NOTE

Oleic acid's penetration enhancement mechanism involves its insertion into the stratum corneum lipid bilayers at the cis-double bond 'kink', disrupting the crystalline packing order and creating liquid-phase domains through which other molecules can more easily diffuse. this reversible lipid fluidization explains both oleic acid's rapid skin penetration and its capacity to enhance penetration of co-applied actives.

Last Verified: 2026-03-12

Primary Sources: Cosing database,hadgraft et al. oleic acid penetration enhancement study,cir safety assessment