An unsaturated C11 fatty acid listed as a preservative and surfactant, regulated in Annex V.
What it is
Undecylenic acid is 10-undecenoic acid, an unsaturated fatty acid with eleven carbon atoms. It is made industrially from castor oil. CosIng lists it as an antimicrobial, emulsifying and cleansing surfactant, fragrance ingredient and preservative. In the EU it is covered by an entry in Annex V (allowed preservatives).
Where it is used
Found in a small number of products, such as shampoos and cleansers.
Limits of interpretation
The INCI list shows which ingredients are present, not how much of each. Above 1%, ingredients are listed in descending order of weight; below 1% the order is free.
See the EU regulation section for the applicable limits. The label does not show the concentration actually used.
Functions
- Antimicrobial
- Preventing and/or slowing down microbial growth.
- Surfactant – emulsifying
- Helping suspensions or dispersions of liquids in a second liquid by reducing the surface tension of the substances to be emulsified.
- Fragrance
- Imparting an odour or taste. Creating a perceivable pleasant smell and/or masking a bad smell.
- Preservative
- Exclusively or mainly intended to inhibit the development of micro-organisms in the cosmetic product. All authorised preservatives are substances in the positive list of Annex V to the Cosmetics Regulation 1223/2009.
- Surfactant – cleansing
- Wetting body surfaces, emulsifying or solubilizing oils, and suspending soil (generally, such ingredients contribute to the foaming and lathering properties of cleansing products).
EU regulation
- Maximum concentration
- 0.2% (as acid)
- As of
- 3 November 2026 · (EC) 2009/1223