If you have ever wondered why some oils absorb instantly while others sit on the skin for hours, why rosehip oil oxidises faster than jojoba, or why a formula that works beautifully for dry skin breaks out someone with oily skin — the answer almost always comes down to fatty acids.
Fatty acids are the primary structural components of vegetable oils and butters. They determine how an oil feels on the skin, how quickly it absorbs, how long it stays stable on the shelf, and which skin types it is most compatible with. Understanding fatty acid profiles is one of the most powerful skills a cosmetic formulator can develop — and this guide is designed to give you a complete, practical reference you can return to every time you are building a new formula.
What Are Fatty Acids?
Fatty acids are long-chain carboxylic acids that form the building blocks of fats and oils. In cosmetic formulation, they are most relevant as the constituent components of triglycerides — the molecular form in which most vegetable oils and butters exist. When a triglyceride is broken down (either in the skin or during processing), it releases three fatty acid chains and a glycerol backbone.
Every carrier oil and butter has a characteristic fatty acid profile — a specific ratio of different fatty acids that gives it its unique properties. No two oils have exactly the same profile, which is why each oil behaves differently in a formula and on the skin.
Fatty acids are classified in two primary ways:
By saturation: A saturated fatty acid has no double bonds in its carbon chain — all carbons are fully "saturated" with hydrogen atoms. A monounsaturated fatty acid has one double bond. A polyunsaturated fatty acid has two or more double bonds. The degree of saturation has a direct impact on the oil's texture, melting point, and oxidative stability.
By chain length: Short-chain fatty acids (fewer than 8 carbons) are rare in cosmetic oils. Medium-chain fatty acids (8–12 carbons) include caprylic and capric acid, found in MCT oil. Long-chain fatty acids (14–22 carbons) make up the majority of cosmetic oils and include oleic, linoleic, palmitic, stearic, and most others discussed in this guide.
The Five Fatty Acids Every Formulator Needs to Know
1. Oleic Acid (Omega-9) — C18:1
Classification: Monounsaturated fatty acid. Carbon chain: 18 carbons, 1 double bond.
Oleic acid is the most abundant fatty acid in most carrier oils and is responsible for the rich, nourishing feel that characterises oils like avocado, argan, and olive. It has a relatively large molecular structure that allows it to penetrate the skin's lipid barrier effectively, making it particularly beneficial for dry, mature, and dehydrated skin types.
Because oleic acid is monounsaturated (one double bond), it is moderately stable — more resistant to oxidation than polyunsaturated fatty acids, but less stable than saturated fatty acids. Oils high in oleic acid typically have a shelf life of 12–24 months with appropriate antioxidant protection.
Skin feel: Rich, slightly heavy, slow to absorb. Best for: Dry, mature, dehydrated skin. Comedogenic tendency: Moderate to high in high concentrations. Key SSC oils: Argan Oil (~46% oleic), Avocado Oil (~65% oleic), Macadamia Oil (~58% oleic), Olive Oil (~70% oleic), Sweet Almond Oil (~69% oleic).
2. Linoleic Acid (Omega-6) — C18:2
Classification: Polyunsaturated fatty acid. Carbon chain: 18 carbons, 2 double bonds.
Linoleic acid is the most important fatty acid for skin barrier function. It is an essential fatty acid — meaning the human body cannot synthesise it and must obtain it from diet or topical application. In the skin, linoleic acid is a key structural component of ceramides, the lipid molecules that hold skin cells together and maintain the integrity of the skin barrier.
Research has shown that people with acne-prone and oily skin tend to have lower levels of linoleic acid in their sebum, which contributes to the formation of comedones. This is why linoleic-rich oils are often better tolerated by oily and acne-prone skin types than oleic-rich oils.
The trade-off is stability: with two double bonds, linoleic acid is significantly more susceptible to oxidation than oleic acid. Oils high in linoleic acid require careful storage (cool, dark, away from air) and benefit from antioxidant protection such as Vitamin E (Tocopherol).
Skin feel: Lightweight, fast-absorbing, dry finish. Best for: Oily, acne-prone, combination, and barrier-compromised skin. Comedogenic tendency: Low. Key SSC oils: Rosehip Oil (~45% linoleic), Hemp Seed Oil (~55% linoleic), Evening Primrose Oil (~72% linoleic), Blackcurrant Seed Oil (~47% linoleic), Safflower Oil (~75% linoleic), Sunflower Oil (~65% linoleic).
3. Palmitic Acid — C16:0
Classification: Saturated fatty acid. Carbon chain: 16 carbons, 0 double bonds.
Palmitic acid is the most common saturated fatty acid in nature and is a natural component of human sebum. Because it is already present in the skin's own lipid matrix, it is well-tolerated by most skin types. It contributes to the occlusive properties of an oil or butter — forming a protective layer on the skin surface that reduces transepidermal water loss (TEWL).
Being fully saturated, palmitic acid is highly stable and resistant to oxidation. Oils and butters high in palmitic acid have excellent shelf life and are less prone to rancidity.
Skin feel: Rich, protective, slightly waxy. Best for: Dry, mature, sensitive skin. Comedogenic tendency: Moderate. Key SSC sources: Shea Butter (~4–7% palmitic), Mango Butter (~3–10% palmitic), Cocoa Butter (~25% palmitic), Sweet Almond Oil (~7% palmitic).
4. Stearic Acid — C18:0
Classification: Saturated fatty acid. Carbon chain: 18 carbons, 0 double bonds.
Stearic acid is a long-chain saturated fatty acid found in high concentrations in solid butters, particularly shea and cocoa butter. It is responsible for the firm, waxy texture of these butters and contributes significantly to their melting point. In formulation, stearic acid acts as an emollient and occlusive agent, and is also used as a thickener and emulsifier in its own right.
Like palmitic acid, stearic acid is a natural component of human sebum and is generally well-tolerated. It is highly stable due to its saturated structure, contributing to the long shelf life of stearic-rich butters.
Skin feel: Firm, waxy, protective. Best for: Dry, mature skin; body butters and balms. Comedogenic tendency: Low to moderate. Key SSC sources: Shea Butter (~35–45% stearic), Cocoa Butter (~35% stearic), Mango Butter (~38–45% stearic), Kokum Butter (~54% stearic).
5. Lauric Acid — C12:0
Classification: Medium-chain saturated fatty acid. Carbon chain: 12 carbons, 0 double bonds.
Lauric acid is the dominant fatty acid in coconut oil (~50%) and is responsible for many of its distinctive properties. It has a smaller molecular size than most long-chain fatty acids, which allows it to penetrate the hair shaft effectively — making it particularly valuable in hair care formulations. On the skin, lauric acid has a light, fast-absorbing feel compared to longer-chain saturated fatty acids.
Lauric acid is also highly comedogenic (comedogenic rating 4 out of 5), which is why coconut oil is well-known for causing breakouts in acne-prone individuals. This does not make it a poor ingredient — it simply means it should be used selectively, at appropriate concentrations, and for appropriate skin types.
Skin feel: Light, fast-absorbing for a saturated fat. Best for: Hair care, body products, dry and normal skin. Comedogenic tendency: High (4/5). Key SSC sources: Coconut Oil (~50% lauric).
Master Fatty Acid Reference Table: SSC Carrier Oils and Butters
The following table provides fatty acid profile data for the key oils and butters in the SSC catalogue. Values are approximate and may vary slightly between batches depending on growing conditions and processing. Use this table as a formulation reference — not as a substitute for the specific COA data for your batch.
| Oil / Butter | Oleic (C18:1) % | Linoleic (C18:2) % | Palmitic (C16:0) % | Stearic (C18:0) % | Other Notable FA | Comedogenic Rating | Shelf Life |
|---|---|---|---|---|---|---|---|
| Jojoba Oil | ~11% (as eicosenoic) | <1% | <1% | <1% | ~70% Gadoleic (C20:1) — liquid wax, not a true oil | 2/5 | 2–5 years |
| Rosehip Oil | 14–20% | 44–50% | 3–5% | 1–3% | ~30–35% α-Linolenic (C18:3, Omega-3) | 1/5 | 6–12 months |
| Argan Oil | 43–49% | 29–36% | 11–15% | 4–7% | High unsaponifiables (~1%): sterols, tocopherols | 0/5 | 18–24 months |
| Avocado Oil | 60–70% | 10–15% | 10–16% | 1–2% | High in Vitamin E and phytosterols | 3/5 | 12–18 months |
| Sweet Almond Oil | 62–72% | 20–28% | 6–8% | 1–3% | Balanced oleic/linoleic ratio; versatile | 2/5 | 12–18 months |
| Hemp Seed Oil | 10–16% | 52–62% | 5–7% | 2–3% | ~17% α-Linolenic (Omega-3); ideal 3:1 Omega-6:Omega-3 ratio | 0/5 | 6–12 months |
| Evening Primrose Oil | 6–10% | 68–74% | 5–8% | 1–3% | ~9% GLA (Gamma-Linolenic Acid, C18:3 Omega-6) | 2/5 | 6–12 months |
| Prickly Pear Seed Oil | 14–18% | 58–65% | 10–14% | 3–5% | Exceptionally high Vitamin E (~150 mg/100g); among the richest sources | 0/5 | 12–18 months |
| Sea Buckthorn Oil | 15–30% | 30–40% | 25–35% | 1–2% | Unique ~35% Palmitoleic (C16:1); deep orange colour from carotenoids | 1/5 | 12–18 months |
| Pomegranate Seed Oil | 4–8% | 4–8% | 2–4% | 1–2% | ~70–80% Punicic Acid (C18:3, conjugated Omega-5) — unique to pomegranate | 1/5 | 12–18 months |
| Raspberry Seed Oil | 10–15% | 50–55% | 2–4% | 1–3% | ~29% α-Linolenic (Omega-3); high natural Vitamin E | 0/5 | 6–12 months |
| Tamanu Oil | 38–44% | 28–34% | 12–15% | 12–15% | Unique calophyllolide and lactone content; strong green colour and scent | 2/5 | 12–18 months |
| Coconut Oil | 5–8% | 1–3% | 8–11% | 2–4% | ~50% Lauric (C12:0); ~20% Myristic (C14:0); highly saturated | 4/5 | 2–3 years |
| Shea Butter | 40–55% | 3–8% | 4–7% | 35–45% | High unsaponifiables (~5–17%): triterpenes, lupeol, cinnamic acid esters | 0/5 | 2 years |
| Mango Butter | 38–50% | 1–5% | 3–10% | 38–45% | Smooth, non-greasy skin feel despite high saturated content | 2/5 | 2 years |
| Cocoa Butter | 30–37% | 2–4% | 24–28% | 32–37% | Very hard at room temperature; melts at skin temperature | 4/5 | 2–3 years |
Note: Fatty acid values are approximate ranges based on published literature. Actual values may vary by batch, origin, and processing method. Always refer to the COA for your specific batch. Comedogenic ratings are based on the widely referenced Fulton comedogenicity scale and are indicative only — individual skin responses vary.
How to Use Fatty Acid Profiles in Formulation
Understanding fatty acid profiles allows you to make deliberate, informed decisions about which oils to include in a formula — and at what concentrations. Here are the key principles to apply.
Match the fatty acid profile to the skin type. Oily and acne-prone skin generally benefits from linoleic-dominant oils (rosehip, hemp, safflower, evening primrose) because they are lightweight, non-comedogenic, and support barrier function without adding excess oleic acid. Dry and mature skin benefits from oleic-dominant oils (argan, avocado, macadamia, sweet almond) because they penetrate the lipid barrier and provide rich nourishment.
Balance stability with performance. Highly polyunsaturated oils (rosehip, hemp, evening primrose) are the most skin-active but also the most prone to oxidation. When using them in formulas, always include an antioxidant — Vitamin E (Tocopherol) at 0.1–0.5% is the standard choice. Saturated oils and butters (coconut, shea, cocoa) are the most stable and have the longest shelf life.
Blend for texture and performance. Rather than using a single oil, most professional formulas blend two or three oils to achieve the desired balance of skin feel, absorption rate, skin type compatibility, and stability. A common approach is to combine one oleic-dominant oil for richness, one linoleic-dominant oil for lightness and barrier support, and one stable saturated oil or butter for texture and shelf life.
Consider the unsaponifiable fraction. Beyond fatty acids, oils also contain an unsaponifiable fraction — compounds that do not convert to soap when treated with alkali. This fraction includes sterols, tocopherols, polyphenols, carotenoids, and other bioactive compounds that contribute to an oil's skin benefits. Shea butter is notable for its exceptionally high unsaponifiable content (5–17%), which contributes to its well-documented skin-conditioning properties.
Frequently Asked Questions
Why does rosehip oil oxidise so quickly?
Rosehip oil is approximately 75–85% polyunsaturated fatty acids (linoleic + alpha-linolenic), each of which contains multiple double bonds. Double bonds are reactive sites that are susceptible to attack by oxygen, light, and heat — a process called oxidative rancidity. The more double bonds, the faster the oil oxidises. Store rosehip oil in a dark, cool location, keep it tightly sealed, and add 0.1–0.5% Vitamin E to any formula containing it.
Is jojoba oil really an oil?
Technically, no. Jojoba is a liquid wax ester — a different molecular structure from triglyceride-based oils. This is why jojoba has an exceptionally long shelf life (2–5 years), does not go rancid in the same way as triglyceride oils, and has a unique skin feel. Its fatty acid profile (dominated by eicosenoic and gadoleic acid) is also unlike any other cosmetic oil.
What is the difference between oleic and linoleic acid for skin?
Oleic acid (Omega-9) is a monounsaturated fatty acid that penetrates the skin's lipid barrier readily, making it nourishing and moisturising — but it can be comedogenic at high concentrations for some skin types. Linoleic acid (Omega-6) is a polyunsaturated essential fatty acid that is a structural component of ceramides and is particularly beneficial for barrier-compromised and acne-prone skin. In general: oleic for dry/mature skin, linoleic for oily/acne-prone skin.
Does a high comedogenic rating mean I should never use the ingredient?
No. Comedogenic ratings are a useful guide, not an absolute rule. They were originally determined by applying neat ingredients to rabbit ears — a test method that does not accurately reflect how diluted ingredients behave in a finished formula. Cocoa butter has a high comedogenic rating but is widely used in body products without issue. The key factors are: the concentration used in the final formula, the skin type of the user, and the overall formula composition.
Source Your Oils and Butters From SSC
Every oil and butter in this guide is available from The Skin Science Company — cosmetic grade, with COA and SDS documentation, and dispatched within 2–3 business days across Australia.
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All products from The Skin Science Company are intended for cosmetic use only. Fatty acid values are approximate and sourced from published literature; always refer to your batch COA for precise data. Nothing in this article constitutes medical or therapeutic advice.