Oleic Acid.

What it does

In cosmetics it works as a rich emollient and, in small amounts, an emulsifier; because it has only one double bond it produces heavier, more occlusive oils than linoleic acid.

Benefits

• Rich, nourishing emollient that softens and conditions dry or mature skin
• Acts as an emulsifier/emulsion stabilizer in small amounts in formulas

Side effects

• Considered comedogenic, so oleic-rich oils can clog pores and worsen breakouts on acne-prone skin
• Well documented as a penetration enhancer that can disrupt the stratum corneum barrier, which may increase irritation or sensitivity for some, especially on already-compromised skin
• Sits within the C11-C24 fatty-acid range that lipid-dependent Malassezia yeast can feed on, so it is generally flagged as a potential fungal-acne (Malassezia folliculitis) trigger

Who it's for

Dry or mature skin and hair wanting a rich, occlusive oil

Who should be careful

Acne-prone, barrier-impaired, or fungal-acne (Malassezia folliculitis)-prone skin should prefer linoleic-rich oils instead