Decyl Oleate

Decyl Oleate is a lightweight emollient ester made by joining decyl alcohol and oleic acid. It feels silky, spreads easily, and helps dissolve pigments.

The Cosmetic Ingredient Review looked at it in 1982 and again in 2015 and concluded both times that it is safe as used when formulated to be non-irritating.

Reported use levels range from 0.1% or less to over 50% depending on the product type.

Irritation and allergy risk is also low: undiluted single applications caused little or no irritation in rabbit skin and eye tests, it was not a sensitizer in guinea pigs at 15%, and repeat insult patch tests at 1-5% showed no sensitization.

This ingredient does have a comedogenic rating of 3 from Fulton's rabbit ear assay. Keep in mind that rabbit ear models tend to overstate what happens on human skin and finished products behave differently than raw ingredients.

As for fungal acne, this ingredient has supposed the growth of Malassezia furfur and sympodialis (but not M. globosa or M. restricta) in direct testing.