Undeceth-9
AKA “Undecyl Alcohol Ethoxylate, Undeceth-9
Surfactant
Ingredient Facts
Undeceth-9
AKA: Undecyl Alcohol Ethoxylate
Surfactant · Emollient · EWG: 4
Synthetic
Emollient
Cleanser
Emulsifier
Skin Conditioner
Not Clean
Poly(oxy-1,2-ethanediyl), .alpha.-hydroxy-.omega.-(undecyloxy)- (9 mol EO average molar ratio)
Effective at 1.6%
CAS #
9002-92-0; 68439-50-9; 5274-68-0; 9004-95-9; 9005-00-9; 4536-30-5; 3055-93-4; 3055-94-5; 3055-95-6
See origin →
Functions
Skin Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Emollient
Fills in the tiny cracks between skin cells to make everything feel smooth and soft. The "silky finish" ingredient.
Cleansing
Makes oil and water mix so dirt, makeup, and sunscreen can actually be washed away. The reason your face wash foams.
Emulsifying
Forces oil and water to stay mixed instead of separating into layers. The unsung hero holding your lotion together.
Locks In Moisture
Traditional Use
A non-ionic synthetic emulsifier developed through ethoxylation in the mid-20th century. Designed to improve the stability and sensory properties of cosmetic formulations.
Skin Types
all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
EWG
4
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not a Sensitizer
medical-approval
all-shades-safe
Concentration Guide
0.2%
3.0%
0%4%
Effective Range
CIR reported use: 0.7-2 | 1-3 | 0.2-3
Regulatory Status
USApermitted
EUrestricted
JAPANrestricted
CANADArestricted
Verified Jun 2026
Data: CosIng · EWG · CIR