Facial oil guide: the science of face oils, comedogenicity, and how to choose

Facial oils occupy a unique position in skincare: they are either enthusiastically recommended as a cornerstone of hydration, or avoided entirely by acne-prone and oily skin users. The truth is more nuanced than either position. Here is the complete guide.

The chemistry of facial oils

Fatty acid composition

All plant-derived facial oils are mixtures of triglycerides — glycerol backbones esterified with fatty acids. The specific fatty acid composition determines the skin behavior of each oil:

Linoleic acid (C18:2, omega-6):
Polyunsaturated fatty acid; lightweight texture; absorbs relatively quickly
Ceramide precursor — linoleic acid is a structural component of the lamellar body lipids that form the skin barrier
Acne-prone skin shows linoleic acid deficiency in sebum — the sebum of acne-prone individuals is disproportionately oleic acid-rich (Letawe 1998); topical linoleic acid helps correct this imbalance
Found at high concentrations in: rosehip oil (~35–40%), hemp seed oil (~55%), evening primrose oil (~75%), sea buckthorn (seed fraction, ~35%)

Oleic acid (C18:1, omega-9):
Monounsaturated fatty acid; richer, slower-absorbing texture
Has greater emollient effect (softer, denser feel on skin) but can worsen acne in susceptible individuals by disrupting the follicular lining similarly to how Malassezia-generated oleic acid drives seborrheic dermatitis
Found at high concentrations in: argan oil (~45%), marula oil (~70%), avocado oil (~70%), olive oil (~75%)

Practical implication: Acne-prone skin is generally better served by linoleic acid-rich oils; dry and mature skin tolerates and benefits from oleic acid-rich oils. This is a spectrum — most oils contain both, in varying ratios.

Saturated fatty acids

Coconut oil is ~90% saturated (lauric, myristic, palmitic acids). These are the most occlusive fatty acids — they create a dense film on the skin surface. Lauric acid has antimicrobial properties against C. acnes in vitro (Nakatsuji 2009), but coconut oil as a facial product is associated with follicular occlusion and comedone formation in many users.

---

The comedogenicity rating problem

"Non-comedogenic" is one of the most misused claims in skincare. The comedogenicity rating scale (0–5) was developed by Kligman and Mills in the 1970s using rabbit ear assays — applying concentrated material to the inner ear of rabbits and scoring follicular plugging. These ratings are:

Not predictive of human skin response — rabbit ear follicles are significantly more reactive than human facial skin; ingredients rated comedogenic in rabbit ears frequently do not cause comedones in humans
Concentration-dependent — an ingredient may cause follicular plugging at 100% concentration but not at the 0.5–2% it appears in a finished product
Individual-dependent — follicular susceptibility varies enormously between individuals; what breaks out one person causes no reaction in another

Practical takeaway: "Comedogenic" ratings on ingredient lists are not reliable predictors of whether a product will cause breakouts. The only reliable test is patch testing a new oil in a small area for 2–4 weeks before full facial use. Individual response is the only meaningful data point.

---

Key facial oils by evidence

Squalane

Source: Originally derived from shark liver oil; now predominantly from sugarcane, olive oil squalene, or amaranth. Squalane is hydrogenated squalene — the saturated, stable form.

Why it's exceptional: Human sebum naturally contains ~10–12% squalene. Squalane is structurally almost identical — it is a branched hydrocarbon, not a fatty acid triglyceride. This means:
It is not hydrolyzed by skin lipases → produces no fatty acids that could disrupt the microbiome or follicle
Extremely low sensitization potential — one of the safest cosmetic ingredients for sensitive skin
Excellent emollient without significant occlusion — spreads easily, does not feel heavy
Photostable and oxidatively stable — does not turn rancid

Skin type suitability: Virtually universal — well-tolerated by acne-prone, sensitive, and dry skin alike.

Rosehip oil

Source: Pressed from the seeds of Rosa canina or Rosa moschata. Rich in linoleic acid (~40%) and alpha-linolenic acid (~30–35%); also contains trans-retinoic acid precursors (beta-carotene; trace retinoic acid).

Evidence: Phetcharat 2015 (RCT, 20 participants with post-surgical scars): rosehip seed oil applied twice daily for 12 weeks significantly improved scar color and texture vs. no treatment. Attribute to linoleic acid barrier support and mild retinoid-like activity.

Photoaging claim: Marketing often emphasizes the retinoid content of rosehip. The actual retinoic acid equivalent is minimal — orders of magnitude lower than even a low-dose retinol serum. Rosehip is a light oil with barrier-supportive linoleic acid, not a meaningful retinoid replacement.

Stability concern: High PUFA content (polyunsaturated fatty acids) makes rosehip oil prone to oxidative rancidity. Store refrigerated; discard after 6 months of opening; do not use rancid oil (oxidized lipids worsen inflammation and may increase acne).

Jojoba oil (technically a wax ester)

Source: Cold-pressed from Simmondsia chinensis seeds. Chemically, jojoba is not an oil (triglyceride) but a liquid wax — long-chain wax esters (C20–C22 alcohol + C20–C22 fatty acid chains).

Unique property: Human sebum contains wax esters as a significant component. Jojoba's wax ester structure closely mimics this — it integrates into the lipid film on the skin surface in a way that triglyceride oils cannot. This explains jojoba's reputation for being "regulating" for oily skin — it provides lipid film without adding conventional oil.

Stability: Wax esters are exceptionally stable to oxidation — jojoba has effectively unlimited shelf life (archaeological specimens retain wax ester integrity). No rancidity concern.

Comedogenicity: Despite oils that "mimic sebum" being presumed comedogenic, jojoba generally does not produce comedones — its wax ester structure is not a substrate for C. acnes lipases in the same way as triglycerides.

Marula oil

Source: Pressed from Sclerocarya birrea kernels. High in oleic acid (~70%), with antioxidant phenolics.

Properties: Exceptionally fast-absorbing for its oleic acid content — partly due to its tocopherol and phytosterol content that aids skin penetration. Rich, emollient feel. Better suited for dry, mature, or non-acne-prone skin due to oleic acid dominance.

Sea buckthorn (Hippophae rhamnoides)

Source: Available in two fractions:
Berry/pulp oil: Deep orange-red from extremely high beta-carotene content; high in palmitoleic acid (omega-7)
Seed oil: More linoleic/alpha-linolenic acid; less pigmented

Evidence: Omega-7 (palmitoleic acid) in the pulp oil has wound healing and mucosal membrane evidence; some skin hydration data. The intense orange pigment transfers to skin — berry fraction oil must be diluted or used very sparingly as a spot treatment.

---

How to use facial oils in a routine

Layering position

Oils are mixed into the lipid phase of the skin. Apply after water-based serums and before or mixed with moisturizer — the oil seals the water-based layers beneath. Never apply oil before water-based actives — the oil film impairs their penetration.

Correct sequence: Cleanser → toner/essence → water-based serum → moisturizer → oil (PM) or SPF (AM — do not use facial oil under chemical SPF; it may reduce SPF uniformity)

Amount

2–4 drops is sufficient for the full face. Pressing into the skin rather than rubbing reduces evaporation loss.

Oil as a moisturizer substitute?

Oils are emollients, not moisturizers. They do not contain humectants (glycerin, hyaluronic acid) that draw water into the skin. An oil alone does not hydrate — it reduces water loss from already-hydrated skin. For maximally hydrated skin, apply a humectant-containing moisturizer before the oil.

---

Do facial oils cause breakouts?

For some individuals, yes — particularly oleic acid-rich oils applied in excess to acne-prone skin, or any oil applied over an existing active breakout (occluding inflamed follicles). For many people, no.

Rules of thumb:
Oily and acne-prone skin: try linoleic-rich oils first (rosehip, hemp seed, squalane)
Patch test on the jawline or inner arm for 2 weeks before committing
Excess application is more likely to cause issues than appropriate amounts

---

Looking for a skincare consultation? Browse med spa providers on MedSpot →