Carrier Oils: The Complete Guide to Base Oils for Skin and Hair

A carrier oil is not a passive vehicle for essential oils. It is an active ingredient in its own right, with its own chemistry, its own evidence base, and its own genuine differences from the oil sitting next to it on the shelf. This is a complete reference to the carrier oils most commonly used in skin and hair care, what they actually contain, and what the evidence for each one actually supports.

Essential oils tend to get the scientific attention in aromatherapy, largely because they are so concentrated and chemically distinctive that they demand careful handling. Carrier oils, sometimes called base oils, are treated by comparison as almost interchangeable, a neutral medium whose main job is to dilute something more interesting. That reputation is not deserved. Carrier oils are fixed, fatty oils, pressed or extracted from seeds, kernels or fruit, and their composition of fatty acids, sterols, tocopherols and other minor constituents varies enormously between one plant source and another. Two oils that look identical in a bottle can behave very differently on skin, and the difference is chemistry, not marketing.

What a carrier oil actually is

Chemically, most carrier oils are triglycerides: three fatty acid chains attached to a glycerol backbone. The specific fatty acids present, and their proportions, determine almost everything practically relevant about an oil, including how quickly it absorbs, how heavy or light it feels, how stable it is against oxidation, and how likely it is to sit on the skin’s surface rather than penetrating it. Jojoba is a notable exception to this general rule, and we will come back to why that matters when we reach it below.

Two families of fatty acid come up repeatedly in this article. Oleic acid is a monounsaturated fatty acid associated with richer, more emollient oils that tend to penetrate the skin’s outer layers more readily. Linoleic acid is a polyunsaturated omega-6 fatty acid associated with lighter, faster-absorbing oils that appear to play a genuine role in supporting the skin’s own barrier lipids, since linoleic acid is itself a structural component of the ceramides that hold the outer skin barrier together. Oils with a very high proportion of saturated fatty acids, coconut oil being the clearest example in this list, behave differently again, and are considerably more likely to sit on the surface or clog pores in people prone to congestion.

That last point touches on comedogenicity, the tendency of an oil to contribute to clogged pores and breakouts. Comedogenicity ratings, generally given on a scale from 0 (will not clog pores) to 5 (highly likely to clog pores), are widely quoted in skincare writing and worth using as a rough guide, but they originate largely from older rabbit-ear assays from the 1980s rather than a large, standardised programme of modern human testing, and individual skin varies considerably in how it actually responds. Treat the ratings below as a reasonable starting point for skin prone to congestion, not as a precise, universally applicable measurement.

At a glance

Almond, sweet (Prunus dulcis)

Sweet almond oil is dominated by oleic acid, typically in the range of 65 to 70 per cent, with linoleic acid making up most of the remainder, alongside a genuinely useful amount of vitamin E. It is a gentle, well-tolerated, moderately rich emollient, widely used in massage and body oils largely because it glides well and rarely causes irritation. It does not have a large body of dedicated clinical trials behind it; its reputation rests more on a long history of safe cosmetic use and a fatty acid profile that behaves predictably than on dramatic research findings, and that is a perfectly respectable basis for an ingredient to be genuinely useful.

Apricot kernel (Prunus armeniaca)

Chemically similar to sweet almond oil, with a comparable oleic and linoleic acid profile and a good vitamin E content, apricot kernel oil is often marketed as a lighter alternative for sensitive or easily congested skin. The evidence base is thin in the same way as sweet almond oil’s; it is a sound, low-risk emollient rather than a heavily researched active ingredient.

Argan (Argania spinosa)

Argan oil contains oleic acid at roughly 43 to 49 per cent and linoleic acid at roughly 29 to 36 per cent, alongside a distinctive tocopherol (vitamin E) profile that differs from most other plant oils. It is one of the better-researched oils in this list: a controlled trial in postmenopausal women found that both dietary and cosmetic argan oil use were associated with improved skin elasticity over a defined period, and its fatty acid and antioxidant content give it a plausible mechanism for that result. Much of the wider “argan oil for hair shine” marketing is not backed by trials of similar quality, but the skin elasticity research is a genuine, specific piece of evidence rather than folklore.

Avocado (Persea americana)

Avocado oil is rich in oleic acid, generally in the range of 50 to 70 per cent, and is notable for an unusually high proportion of unsaponifiable matter, including phytosterols, compared with most other carrier oils. Animal studies have found that avocado oil can promote collagen synthesis and support wound healing when applied topically, which is interesting and mechanistically plausible, but the direct human clinical evidence remains limited. It is a genuinely rich, heavier oil, and its higher comedogenic rating means it suits dry body skin and hair better than acne-prone facial skin.

Castor (Ricinus communis)

Castor oil is chemically unusual: ricinoleic acid makes up somewhere around 85 to 95 per cent of its fatty acid content, a proportion not seen in any other common carrier oil. That unique fatty acid gives castor oil its very high viscosity and strong occlusive, moisture-sealing properties, which is a real and useful function. Its popular reputation for dramatically thickening hair or accelerating hair growth considerably outpaces the direct clinical evidence for either claim, as we discuss in more detail in our piece on our own twice-weekly hair oil. Ricinoleic acid does have plausible anti-inflammatory activity in laboratory research, but that has not yet translated into strong human trial evidence for the growth claims most commonly made.

Coconut (Cocos nucifera)

Coconut oil is unusual among carrier oils in being highly saturated, dominated by lauric acid at roughly 45 to 50 per cent alongside a significant proportion of myristic acid. That saturated, medium-chain structure is precisely what allows coconut oil to penetrate the hair shaft rather than simply coating the surface, and a frequently cited comparative study found that coconut oil reduced hair protein loss during washing significantly more effectively than mineral oil or sunflower oil, for both damaged and undamaged hair. This is one of the stronger, more specific pieces of evidence behind any carrier oil in this list. On facial skin, the same saturated, occlusive quality that makes coconut oil so effective on hair also gives it one of the higher comedogenic ratings here, and it is generally a poor choice for skin prone to congestion or breakouts.

Evening primrose (Oenothera biennis)

Evening primrose oil is notable for its gamma-linolenic acid (GLA) content, typically around 8 to 14 per cent, alongside a high proportion of ordinary linoleic acid. GLA is a genuinely interesting fatty acid with a plausible role in skin barrier and inflammatory signalling, and oral evening primrose oil has been studied, with mixed results, for conditions including eczema. The topical, cosmetic use of evening primrose oil has considerably less direct clinical evidence behind it than the oral research, so claims made for a face or body oil containing it should be read with more caution than the ingredient’s underlying chemistry might suggest.

Grapeseed (Vitis vinifera)

Grapeseed oil is very high in linoleic acid, often 58 to 78 per cent, which gives it a notably light, fast-absorbing, slightly astringent feel compared with heavier, more oleic-dominant oils. It also contains proanthocyanidins, antioxidant polyphenols associated with the wider research interest in grape seed extract. Its low comedogenic rating and light texture make it a popular choice for massage oils and blends intended to feel non-greasy, though as with several oils in this list, much of its cosmetic reputation rests on plausible chemistry rather than a large body of dedicated topical trials.

Hemp seed (Cannabis sativa)

Hemp seed oil, pressed from the seeds rather than containing meaningful cannabinoid content, has an unusually favourable fatty acid ratio for skin barrier purposes: roughly 55 to 60 per cent linoleic acid alongside 15 to 20 per cent alpha-linolenic acid, an omega-3, giving it close to the 3:1 omega-6 to omega-3 ratio sometimes described as ideal for skin. Small trials investigating hemp seed oil for eczema and dry skin have produced encouraging but mixed results, generally in dietary rather than purely topical form, so its excellent chemistry is somewhat ahead of the confirmatory clinical evidence at this stage.

Jojoba (Simmondsia chinensis)

Jojoba deserves its own note because it is not, strictly speaking, an oil at all in the triglyceride sense that applies to everything else on this list. It is a liquid wax ester, composed of long-chain fatty acids bonded to long-chain fatty alcohols rather than to glycerol. That structural difference is precisely what makes jojoba unusually close in composition to human sebum, the skin’s own natural oil, which is the most plausible explanation for its excellent stability, its resistance to oxidation compared with true oils, and its consistently low comedogenic rating across most reported skin types. It is one of the few carrier oils where the marketing claim, “similar to your skin’s own oil,” is genuinely, chemically accurate rather than a loose approximation.

Olive (Olea europaea)

Olive oil is very high in oleic acid, frequently 55 to 83 per cent depending on cultivar and grade, alongside a notable squalene content. Its history of cosmetic and culinary use is genuinely ancient, but its modern skincare reputation has run somewhat ahead of more recent evidence: a review of natural oils and skin barrier function noted that olive oil has, in several studies, been associated with impaired skin barrier function and increased water loss when used on already compromised skin, including in research on infant skin, in contrast to more favourable results for sunflower oil in similar comparisons. This does not mean olive oil is unsafe for ordinary cosmetic use on healthy adult skin, but it is a useful corrective to the assumption that a longer culinary history automatically makes an oil the better cosmetic choice.

Rosehip seed (Rosa canina and related species)

Rosehip seed oil, pressed from the seeds inside the fruit rather than the petals, contains a relatively high proportion of linoleic and alpha-linolenic acid alongside trace amounts of naturally occurring retinoic acid precursors and vitamin C. It has been investigated in small trials for scarring, stretch marks and photoaged skin, generally with modest, encouraging rather than dramatic results, and its polyunsaturated fatty acid profile gives it a genuine mechanistic reason to support barrier repair. As with several oils here, the trial evidence is real but limited in scale, which argues for treating it as a promising, plausible ingredient rather than a proven scar treatment.

Sea buckthorn (Hippophae rhamnoides)

Sea buckthorn is unusual enough, and different enough between its seed oil and pulp oil, that it earns its own full Botanical Library monograph rather than a short summary here. In outline, seed oil carries a more conventional polyunsaturated fatty acid profile suited to lightweight formulations, while pulp oil is unusually rich in palmitoleic acid and deep carotenoid pigment, and the two should be thought of as related but genuinely distinct ingredients.

Sunflower (Helianthus annuus)

Standard, high-linoleic sunflower oil is dominated by linoleic acid, often 60 to 70 per cent, though high-oleic sunflower cultivars bred more recently for cooking have a substantially different, oleic-dominant profile, which is a useful reminder that a plant’s common name does not guarantee a single fixed chemistry. For skincare purposes, high-linoleic sunflower oil has some of the better direct evidence in this entire list for supporting skin barrier function: research reviewed alongside olive oil found sunflower oil associated with improved barrier measures where olive oil was associated with impairment, in studies including vulnerable infant skin. It is unglamorous compared with more exotic oils on this list, and arguably better supported than several of them.

Choosing a carrier oil for your own routine

None of this is intended to produce a single correct answer, because the right carrier oil depends on what you are actually trying to do. For a scalp and hair oil like the one described in our own twice-weekly ritual, a blend leaning on coconut oil’s genuine hair-protein evidence, lightened and enriched with sweet almond and castor oil, makes good sense. For facial skin prone to congestion, a lighter, lower-comedogenic oil such as grapeseed, hemp seed or jojoba is generally the safer starting point than a rich, highly occlusive oil such as coconut or avocado. For an aromatherapy blend intended purely as a pleasant carrier for essential oils such as lavender, a light, stable, well-tolerated oil that will not compete with or overwhelm the aromatic material is usually the better technical choice than the most fashionable oil currently on the shelf.

What is not proven

It is worth being plain about the overall pattern running through this article. A handful of carrier oils, coconut and argan being the clearest examples, have genuine, specific human trial evidence behind particular claims. Several more, including avocado, rosehip seed, hemp seed and evening primrose, have plausible chemistry and encouraging early or mixed evidence that has not yet developed into a large, confirmatory body of research. And some of the oldest, most culturally embedded oils, olive oil in particular, carry cosmetic reputations that outrun what the more recent comparative research actually supports. None of that makes the less-proven oils useless; fatty acid chemistry alone gives a reasonable case for most of them as sound, low-risk emollients. It simply means the confident, specific claims often printed on the label deserve the same scrutiny we try to apply to everything else in this Library.

Frequently asked questions

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References

• Vaughn, A.R., Clark, A.K., Sivamani, R.K. & Shi, V.Y. (2018). Natural oils for skin-barrier repair: ancient compounds now backed by modern science. American Journal of Clinical Dermatology, 19(1), 103-117. doi:10.1007/s40257-017-0301-1
• Rele, A.S. & Mohile, R.B. (2003). Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. Journal of Cosmetic Science, 54(2), 175-192.
• Boucetta, K.Q. et al. (2015). The effect of dietary and/or cosmetic argan oil on postmenopausal skin elasticity. Clinical Interventions in Aging, 10, 339-349. doi:10.2147/CIA.S71684
• Fulton, J.E. (1989). Comedogenicity and irritancy of commonly used ingredients in skin care products. Journal of the Society of Cosmetic Chemists, 40, 321-333. (Origin of the widely quoted comedogenicity scale; note its age and original animal-model methodology.)