Oleic Acid
A monounsaturated omega-9 fatty acid. At low concentrations works as a mild emollient. At meaningful concentrations (typical of olive, avocado, nut oils) it increases stratum corneum permeability and disrupts the barrier – especially in people with atopic dermatitis, rosacea and fungal acne. Comedogenicity rating 2.
Evidence by route
Topical application
Two-sided profile: on dry and normal skin – a gentle emollient in barrier formulas. On sensitive, acne-prone or compromised-barrier skin it raises TEWL and triggers flare-ups (Danby 2013, Vaughn 2018). Also feeds Malassezia – not suitable for fungal acne.
- Danby SG et al. Effect of olive and sunflower seed oil on the adult skin barrier. Pediatr Dermatol 2013;30(1):42-50. PMID 22995032
- Vaughn AR et al. Skin-aging and healthy skin properties of plant oils. J Clin Aesthet Dermatol 2018. PMID 28707186
How to read tiers A–F
- BLimited evidence. One RCT or several controlled studies with limitations
Tolerability and safety
- Irritation potential
- Medium
- Allergen risk
- Low
- Pregnancy
- Safe
- Suitable for
- Dry, Normal
- Use with caution
- Oily, Combination, Sensitive
About this ingredient
Oleic Acid is a monounsaturated omega-9 fatty acid with 18 carbon atoms (C18:1). Found in high concentration in olive, sunflower, almond, avocado oils. In skin – a component of sebum (15–20%) and intercellular lipids. Mechanism. Emollient and penetration enhancer – integrates into stratum corneum lipids, loosens their structure, facilitates penetration of other actives. At moderate concentrations restores the hydrolipid barrier. At high concentrations disrupts the barrier (increases TEWL), which is used in pharmaceutical formulas to enhance drug absorption. Where applied. Creams and oils for dry and mature skin, Castile soap, lipsticks, balms. Concentration 1–25%, in pure oils up to 80%. Evidence base. Danby 2013 clinical study (n=19) showed that oleic acid disrupts the barrier in newborns and atopic dermatitis patients – reduces hydration and increases TEWL. AAD 2024 recommends avoiding oleic-rich oils (especially olive) in childhood atopy. Linoleic acid, by contrast, restores the barrier. Safety. Comedogenicity 2 of 5 – in acne patients may cause comedones. On dry and mature skin without acne – safe. Pregnancy and lactation – topically safe. Usable neat in massage oils for stretch marks, but avoid on inflamed skin and in atopy.
Frequently asked questions
Is Oleic Acid safe during pregnancy?
Oleic Acid is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
What skin types is Oleic Acid for?
Oleic Acid suits: dry, normal. Use with caution in: oily, combination, sensitive.
Can Oleic Acid irritate the skin?
Oleic Acid has moderate irritation potential. Sensitive skin may show a transient reaction that usually settles with adaptation.
What is Oleic Acid and what does it do in cosmetics?
A monounsaturated omega-9 fatty acid.
Is Oleic Acid comedogenic?
On the Fulton scale 2/5 – low comedogenicity. For acne-prone skin, a rating of 3 or higher suggests choosing an alternative.
What's the INCI name for Oleic Acid?
The INCI name is Oleic Acid. It may also appear as: Omega-9, C18:1.
See Oleic Acid in a product composition right on the store page
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