Glyceryl Undecylenate

Irritancy: unknownComedogenicity: unknownEmollient

Fungal-acne trigger

The details

Glyceryl Undecylenate is a gentle ester made by joining glycerin and undecylenic acid (a fatty acid pulled from castor oil). In formulations, it pulls double duty as a skin-conditioning emollient and mild preservative. The glycerin side attracts and binds water to support skin hydration and the undeclyenic acid side adds a bit of broad-spectrum antimicrobial activity. Undecylenic acid inhibits the formation of fungal biofilm and the branching filaments that let fungi spread. Typical use concentrations range from 0.1-5%, but it is generally used on the lower end and paired with other mild preservative boosters like caprylyl glycol . On the fungal acne front: This ingredient is described in the patent literature as a Malassezia-active ingredient used to treat an excess of Malassezia on the skin (Malassezia is actually a yeast and not fungal). Though it leans anti-fungal, the leftover Malassezia yeast may feed on the Undecylenic Acid portion of this ingredient. Just know this ingredient may not be a trigger for everyone.