Undecylenic Acid
molecular structure · PubChem
AKA: Undec-10-enoic acid, 10-UNDECENOIC ACID, 112-38-9, 10-Hendecenoic acid, Renselin, Declid, Sevinon, 10-Undecylenic acid, Undecylenate
Synthetic
Preservative
Cleanser
Emulsifier
Acid
Clean
Undec-10-enoic acid; 10-Undecenoic acid
Solubility Insoluble
Formula
C11H20O2
Mol. Weight
184.27
CAS #
112-38-9
Form
Liquid
State
Liquid
Functions
Antimicrobial
Keeps your product from growing bacteria, mold, or yeast. Without these, that jar of cream becomes a petri dish in about a week.
Preservative
Keeps your product from growing bacteria, mold, or yeast. Without these, that jar of cream becomes a petri dish in about a week.
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.
Fights Bacteria
Traditional Use
Derived from castor oil in the early 20th century. Historically used in traditional medicine for fungal infections; later adopted by cosmetic chemists as an antimicrobial and antifungal ingredient in skincare products.
EWG
2
CIR
Safe as used
Pregnancy
Caution
CIR Safety Findings
Not a Sensitizer
medical-approval
all-shades-safe
Concentration Guide
0.2%
0%0%
Reg. Limit
EU regulatory limit: 0.2%. Source: EU Cosmetics Regulation (EC) 1223/2009, Annex V (Preservatives), Entry 18.
Regulatory Agencies
Skin Types
●all-skin-types
Best For
Acne
Pregnancy & Breastfeeding Safe
Caution
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR