Common Name(s): Oleth-25,oleyl alcohol 25-mole ethoxylate,cold-stable nonionic emulsifier

CAS Number: N/a

DESCRIPTION

What It Does: Oleth-25 emulsifies oil-phase ingredients into water-based formulations and solubilises oils and fragrances into aqueous systems, producing stable o/w emulsions and clear microemulsions. the 25-eo chain length sets its hlb value, determining whether it functions best as a primary emulsifier, co-emulsifier, or wetting agent.

Why It's Used: Formulators choose oleth-25 when cold-temperature stability is required — a common failure mode with saturated fatty alcohol ethoxylates (ceteth, steareth) is crystallisation or phase separation at refrigerator temperatures (4–10°c) during storage and shipping. the oleyl chain's cis geometry physically prevents the close-packing needed for crystal formation, ensuring consistent product performance from manufacturing through consumer use. it is also preferred for fragrance solubilisation in clear tonics and mists where a turbid emulsion would be commercially unacceptable.

How It Works: Oleth-25 functions as a surfactant through its amphiphilic architecture: the c18:1 oleyl hydrophobic tail inserts into oil droplets or fragrance molecules while the 25-unit polyethylene glycol chain extends into the water phase, thermodynamically stabilising the interface. the 25 ethylene oxide units provide an hlb of approximately 14 placing it in the o/w emulsification range. crucially, the cis double bond at c9–c10 of the oleyl chain introduces a 30° geometric kink that sterically prevents parallel chain alignment — the prerequisite for crystalline packing — so the ethoxylate remains liquid down to well below 0°c and never forms the waxy precipitates seen with saturated equivalents.

Typically Found In: O/w emulsions,fragrance solubilisers,clear tonic formulas

TECHNICAL DETAILS

Primary Category: Active ingredient – cosmetic active

Secondary Functions: Skin conditioning

Application Areas:

Typical Concentration Range: 1%–20%

SOURCING & ETHICS

Vegan Status: Conditional - feedstock declaration required

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

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier. [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: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Oleyl vs cetyl ethoxylate cold stability: ceteth (c16:0 saturated) ethoxylates crystallise at 10–25°c from efficient parallel chain packing. oleth (c18:1 cis) resists crystallisation below –10°c because the cis double bond introduces a 30° kink at c9 that prevents the parallel chain arrangement required for crystal nucleation. a single double bond provides ~30°c lower crystallisation temperature from geometric prevention of crystal lattice formation — a fundamental principle of lipid biophysics applied to surfactant cold-stability engineering.

Last Verified: 2026-03-12

Primary Sources: Cosing database,oleth-25 oleyl ethoxylate cold stability review