Contents
An anhydrous leave-on blend of lipids. A facial oil is not a moisturiser in the sense most people mean — it contains no water and cannot add any. What it does is slow the water already in the skin from leaving, and supply fatty acids the barrier is built from.
The three jobs a lipid can do
| Job | Mechanism | Ingredients that do it |
|---|---|---|
| Occlusion | Physical film slowing water loss | Mineral oil, petrolatum, squalane, jojoba |
| Emolliency | Filling gaps between surface cells; smoothing | Most plant oils, esters |
| Barrier substrate | Supplying fatty acids the skin uses structurally | Linoleic-rich oils — safflower, sunflower, rosehip, grapeseed |
The third is the interesting one. Skin barrier lipids are ceramides, cholesterol and free fatty acids, and linoleic acid is a component of the ceramides that hold the barrier together. Sebum in acne-prone skin is characteristically low in linoleic acid and high in oleic — which is the basis of the widely repeated advice to favour linoleic-heavy oils on congested skin and treat oleic-heavy ones (coconut, olive, marula) with caution there.
Oils worth distinguishing
- Squalane — hydrogenated squalene, usually from olive or sugarcane. Extremely stable, light, near-universally tolerated, no scent. The safest default.
- Jojoba — technically a liquid wax ester, closest of the common oils to human sebum in structure.
- Rosehip — high linoleic and linolenic, contains trace trans-retinoic acid. Oxidises fast; buy small, keep cold.
- Mineral oil — the most occlusive and least reactive option available, and the one with the worst reputation relative to its record. See mineral oil.
- Essential oils — lavender, tea tree, citrus, ylang-ylang. These are fragrance, not treatment. Citrus oils containing furocoumarins are photosensitising, and oxidised limonene and linalool are among the most common cosmetic contact allergens. An oil blend with a long essential-oil list is a fragranced product.
Using it
Last, or nearly last — an oil applied under a water-based serum blocks it. On damp skin, or over a humectant, so there is water underneath for it to hold. A few drops pressed in, not rubbed.
Facial oil alone on dehydrated skin in dry air is the common mistake: with no water underneath, the occlusive film is sealing in nothing.
Where it sits in the rules
Cosmetic only — FDA primary category (14). Anhydrous, so no preservative is required and most facial oils contain none, which is correct and not a shortcut.
Where it gets legally interesting is claims: an oil marketed as treating eczema or psoriasis is making a drug claim, and an oil marketed with an SPF number would be a sunscreen drug. Neither is available to a cosmetic.
Essential-oil-heavy blends carry the EU fragrance-allergen declaration obligation, and the allergen list requiring individual declaration was substantially expanded by Regulation (EU) 2023/1545 — so a blend that reads as "100% natural" on the front may carry a long allergen tail on the back in EU markets.
Shelf life
Rancidity is the clock. Highly unsaturated oils — rosehip, evening primrose, flax, hemp — oxidise within months and are best kept refrigerated. Squalane, jojoba and mineral oil are stable for years. A sharp, putty-like or crayon smell means oxidation, and oxidised lipids are irritants, so a rancid oil is worse than an inert one. Buy dark glass, buy small.
Related
- Skincare — the shelf this sits on, and the rest of it.
- Cosmetics — what the label is legally allowed to say, and the full catalogue.
- The rest of Treating — Facial Serum · Ampoule · Spot Treatment · Blemish Patch · Retinoid Treatment · Brightening Treatment.
- Cleansing Oil · Body Oil — the same lipids, different briefs.
- mineral oil — the ingredient, and the argument about it.
- Regulatory statements here follow the FDA and EU sources listed on Cosmetics, read 16 August 2026.