Facial Oils Compared

A facial oil is an emollient: it sits on the outer layer of skin and slows the water escaping from it. That is the one job every plant oil does. What separates them is their fatty acid mix and how much human evidence backs anything beyond it.

Two fatty acids matter most. Oils high in linoleic acid, an omega-6 fat the skin uses to build its barrier lipids, tend to suit skin well. Oils high in oleic acid loosen the tightly packed lipids of the outer layer, which is why oleic acid is used in pharmacology to help drugs pass through skin, and why it can work against a barrier that is already weak. The grouping below follows trials in people rather than test-tube results.

Good evidence

Sunflower seed oil has the clearest data. In a study by Danby and colleagues (Pediatric Dermatology, 2013), adults applied sunflower seed oil to one forearm and olive oil to the other for four weeks; sunflower oil kept the outer layer intact and improved hydration. Trials in preterm babies in low-income settings, starting with Darmstadt and colleagues in The Lancet in 2005, found daily sunflower oil massage reduced hospital-acquired infections. That is a narrow population, and a later pilot in healthy newborns hinted that oiling may slow barrier development compared with nothing, so it is no reason to oil every baby. For an adult with dry skin it is a sensible, inexpensive choice.

Coconut oil earns its place for eczema on the body. Small randomised trials found virgin coconut oil improved eczema severity, one in adults against olive oil (Verallo-Rowell and colleagues, Dermatitis, 2008) and one in children against mineral oil (Evangelista and colleagues, International Journal of Dermatology, 2014). The first also measured less Staphylococcus aureus on treated skin. The face is another matter: many people with acne-prone skin find it clogging.

Squalane is a refined, stable emollient made by hydrogenating squalene from olives or sugarcane. Its strength is tolerability; it rarely irritates. As a moisturiser it is ordinary, doing what any light emollient does and no more.

Mixed or limited

Jojoba oil is technically a liquid wax. Wax esters are one component of human sebum, and that resemblance is the basis for claims that it "balances" oil production, which no human trial has shown. It is generally well tolerated and slow to go rancid.

Rosehip seed oil is rich in linoleic acid. Its vitamin A content is usually overstated, since cold-pressed oil holds only small amounts of retinoid-like compounds. A handful of small, mostly unblinded scar studies exist, which falls well short of "fades scars and dark spots".

Argan oil has a few small studies on skin elasticity, several of them combining oral and topical use. It is a pleasant moisturiser, with nothing that sets it apart from cheaper linoleic-rich oils for most people.

Weak or risky

Olive oil belongs here because of the same Danby study: it damaged the integrity of the outer skin layer and caused mild redness within four weeks. The authors advised against it for dry skin and infant massage, especially where there is a family history of eczema.

Tamanu oil gets its anti-inflammatory and antibacterial reputation largely from lab work. There are no good trials showing it treats eczema or dermatitis, and allergic contact reactions to it have been reported.

Evening primrose oil contains gamma-linolenic acid, which is why it was tried for eczema, mainly as an oral supplement. A 2013 Cochrane review found oral evening primrose and borage oil no better than placebo. Topical evidence is sparse, and rubbing it on skin has no plausible route to "hormonal balance".

Marula and grapeseed oils rest on antioxidant claims drawn from what the oil contains, not from measured effects in skin. Fine if you like the feel.

One caution runs across all three groups. The numerical "comedogenic" ratings found online mostly trace back to rabbit-ear tests from the 1970s and 1980s, which overstate clogging and translate poorly to human faces. Treat them as a rough hint. Heavier oils and butters are more likely to cause trouble than light, linoleic-rich ones, and nut-derived oils deserve care if you have a nut allergy.

Essential oils are not carrier oils

Everything above is a carrier oil: a fatty oil pressed from seeds, nuts or fruit. Essential oils such as lavender, tea tree, peppermint and ylang-ylang are concentrated, volatile aroma compounds that behave like fragrance, and several are common causes of allergic contact dermatitis. Tea tree oil grows more allergenic as it oxidises in an opened bottle, and cold-pressed bergamot can cause burns when skin is exposed to sunlight. Tea tree has some acne evidence (a 5 percent gel compared with benzoyl peroxide in a 1990 Australian trial worked more slowly but irritated less), but that was a formulated gel at a fixed strength. Never put an essential oil on skin undiluted, and if you have eczema or sensitive skin, leave them out altogether.

Patch testing a new oil

Dermatologists use a version of this, the repeated open application test, to check products at home.

1. Choose one new oil at a time. Testing two at once makes a reaction impossible to trace.
2. Apply a few drops to a coin-sized area on the inner forearm or the crease of the elbow, morning and evening, without washing it off between applications.
3. Keep going for seven days. Allergic reactions are often delayed, appearing two or three days in rather than within minutes.
4. Check daily for redness, itching, small bumps or swelling. Any of these means the oil is not for you; wash the area and stop.
5. If the arm stays clear, use two or three drops on one side of the jaw for another few days, since facial skin is thinner and more reactive.
6. If you are acne-prone, give the face a further three to four weeks before judging, because clogged pores take that long to show.

A clear test lowers the odds of an allergy but cannot rule out irritation later. If a new oil causes swelling or a spreading rash, or eczema flares and stops responding to a plain moisturiser, stop and see a doctor or dermatologist, who can run formal patch testing to pin down the plant ingredient involved. Keep oils that pass in a cool, dark cupboard with the cap tight, and throw out any bottle that starts to smell sharp or like old crayons, the sign that it has gone rancid.