Antioxidants for the skin: vitamin C, E and ferulic acid explained without exaggeration

Vitamin C serum has become almost a fixture of skincare routines, often accompanied by big promises: "instant radiance", "erases dark spots", "protects from pollution", "rejuvenates". Some of these promises have a basis; others are exaggerated. And there is a detail few people explain: a large proportion of the vitamin C serums on sale may have little effect, because of issues of formulation, stability and storage.

This article explains what antioxidants do for the skin, what research shows about the three most commonly used molecules (vitamin C, vitamin E and ferulic acid) and how to choose and use a product so that it is worthwhile.

Free radicals and oxidative stress: what is at stake

Free radicals (or reactive oxygen species) are unstable molecules that react with everything they find: membrane lipids, proteins such as collagen and elastin, and the cells' own DNA. They form naturally in metabolism, but their production increases greatly with:

• Ultraviolet radiation, especially UVA, which penetrates deeper into the skin.
• Visible and infrared light, to a lesser degree.
• Air pollution, especially fine particles and ozone.
• Tobacco.

The skin has its own antioxidant defence system: vitamin C, vitamin E, glutathione and antioxidant enzymes. But this system becomes depleted with exposure. Studies show that a single sun exposure can significantly reduce vitamin C and E levels in the skin (Thiele et al., 1998).

When free radicals overwhelm the defences, this is called oxidative stress. The consequences build up over years:

• Activation of enzymes that break down collagen (metalloproteinases).
• Low-grade inflammation.
• DNA damage, which contributes to photoageing and skin cancer.
• Stimulation of pigment production.

The logic of topical antioxidants is to reinforce these defences, especially during the day. The logic of sunscreen is different: to stop radiation from reaching the skin. The two strategies add up, but do not replace each other. See Tinted sunscreen: how to choose and how to apply.

Vitamin C: the most studied, the most demanding

Vitamin C is the most abundant antioxidant in the skin, and humans cannot produce it. In the skin, besides neutralising free radicals, it is indispensable for collagen production and interferes with melanin production (Al-Niaimi and Chiang, 2017).

What the evidence shows

• Complementary photoprotection. In laboratory studies and on human skin, topical vitamin C reduces redness and the number of damaged cells after UV exposure. It does not absorb radiation like a UV filter: it neutralises part of the damage that radiation causes.
• Tone and dark spots. By interfering with melanin production, it helps even out tone and slightly lighten dark spots, with a modest, slow effect.
• Fine wrinkles and texture. Small controlled trials showed improvements in fine wrinkles and texture after a few months of use, probably through stimulation of collagen (Traikovich, 1999).
• Radiance. Frequently mentioned by users, it is harder to measure objectively.

Why many serums do little

Pure vitamin C (L-ascorbic acid) is difficult to formulate. Classic studies of absorption in the skin identified conditions necessary for it to penetrate (Pinnell et al., 2001):

• Low pH, below 3.5, so that the molecule is in a form that crosses the stratum corneum.
• Concentration between 10 and 20%. Below 8 to 10% the effect is small; above 20% absorption does not increase but irritation does.
• Stability: on contact with air, light and heat, vitamin C oxidises quickly and loses effectiveness.

That is why the industry developed more stable derivatives (magnesium ascorbyl phosphate, sodium ascorbyl phosphate, ascorbyl glucoside, ascorbyl tetraisopalmitate, among others). They are gentler and more stable, but generally have fewer clinical studies and need to be converted in the skin in order to act. They can be a good option for sensitive skin, with adjusted expectations.

Signs that a serum has oxidised

• Colour that changes from clear or straw-yellow to dark orange or brown.
• Different smell.
• It may leave the skin slightly orange (it is oxidised vitamin C, harmless, but without benefit).

Vitamin E and ferulic acid: the partners

Vitamin E

Vitamin E (alpha-tocopherol) is the skin's main fat-soluble antioxidant: it protects the lipids in cell membranes and in the skin barrier. On its own, it has a modest antioxidant effect when applied topically. Its value lies in its collaboration with vitamin C: the two regenerate each other, prolonging the antioxidant action.

A note: topical vitamin E is a known, although infrequent, cause of allergic contact dermatitis (Kosari et al., 2010). And, contrary to popular belief, applying vitamin E to scars has not shown consistent benefit in studies and may cause irritation (Baumann and Spencer, 1999).

Ferulic acid

Ferulic acid is a plant-derived antioxidant, present in the cell wall of cereals such as rice and wheat bran. It absorbs part of UV radiation and neutralises free radicals, but its most studied role in the skin is another: to stabilise vitamin C and vitamin E.

The C + E + ferulic combination

A 2005 study, carried out on pig skin (a model similar to human skin), tested a solution with 15% L-ascorbic acid and 1% alpha-tocopherol, with and without ferulic acid (Lin et al., 2005):

• The vitamin C and E solution increased by around 4 times the dose of simulated solar radiation needed to cause redness and sunburn cells.
• With ferulic acid, this protection rose to around 8 times.
• Ferulic acid improved the chemical stability of the vitamins and the mixture reduced the formation of thymine dimers, a type of DNA damage caused by UV.

This is one of the most cited scientific bases for antioxidant serums. But it should be read rigorously:

• It is not an SPF. "4 times" or "8 times" does not mean SPF 4 or SPF 8 and does not allow you to skip sunscreen.
• It was a laboratory study, in an animal model, with a specific formula. Other formulas with the same names on the label may have different concentrations, pH and stability.
• The study was carried out by researchers linked to the development of this formulation.

The reasonable message: combining vitamin C, vitamin E and ferulic acid in a well-made formulation reinforces antioxidant protection and stability. Used under sunscreen, it is an extra layer of defence.

Other antioxidants and the oral route

Other topical antioxidants

What about taking antioxidants orally?

The idea of "protecting the skin from the inside out" is attractive, but the evidence is weaker than for topical application, and there are important cautions:

• A diet rich in fruit and vegetables is associated with better health in general, and is the best way to obtain antioxidants.
• High-dose supplements have not shown consistent benefit for the skin and some have shown risks. In a large trial in smokers, beta-carotene supplements increased the incidence of lung cancer (Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group, 1994).
• Oral nicotinamide: in a randomised trial in people with a history of several non-melanoma skin cancers, oral nicotinamide reduced the appearance of new cancers of this type by around 23% during the year of treatment (Chen et al., 2015). It is a specific medical indication for high-risk people, not a beauty supplement, and should be decided with the dermatologist.
• Oral "photoprotective" plant extracts: some have small studies showing a slight reduction in sun sensitivity. They do not replace topical and physical protection.

Before taking supplements, especially at high doses, in pregnancy or with chronic medication, speak to your doctor or pharmacist.

How to choose and use an antioxidant

Choosing

• Pure vitamin C (L-ascorbic acid) at 10 to 20%, for those who tolerate it well and want the form with the most evidence. Sensitive skin can start with 10%.
• Stable derivatives, for sensitive or reactive skin, with more modest expectations.
• Combinations with vitamin E and ferulic acid, which reinforce stability and protection.
• Opaque, airtight packaging, ideally with a small dropper or pump; small bottles run out before they oxidise.
• Price: not a guarantee. What matters is the form, the concentration, the pH and the stability.

To use

• In the morning, after cleansing and before moisturiser and sunscreen. It is during the day that the skin faces the sun and pollution.
• A few drops are enough for the face and neck.
• Sunscreen always on top.
• Keep the bottle closed, away from light and heat; some manufacturers recommend the fridge.
• Throw it away when it darkens noticeably.

Combinations

• With retinoids: you can use vitamin C in the morning and a retinoid at night. Using both at the same time increases the risk of irritation.
• With exfoliating acids: on sensitive skin, avoid applying them at the same time.
• With niacinamide: the idea that they are incompatible comes from old studies in conditions very different from real-life use. Most skin tolerates both well.

Who should be careful

• Very sensitive skin or skin with rosacea: the low pH of pure vitamin C may sting; prefer derivatives or lower concentrations.
• Tendency towards contact dermatitis: vitamin E and some extracts can cause allergy.
• Pregnancy: topical vitamin C is generally considered compatible; check the complete formula with your doctor.

What to expect and when

• Radiance: a few weeks.
• More even tone: 2 to 3 months.
• Fine wrinkles and texture: 3 to 6 months.
• Complementary photoprotection: invisible day to day, but cumulative.

At Luxmed, we help fit antioxidants into a simple routine consistent with your skin, without piling on unnecessary products. In the clinic, some facial treatments include antioxidants in suitable concentrations and formulations.

This article is for information purposes and does not replace a medical consultation. The results of any product vary from person to person.

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