Antioxidant Skincare, Explained: What the Research Actually Says

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What “antioxidant” actually means, biologically speaking
Vitamin C: the most researched, and the most misunderstood
The “combine your antioxidants” research is real, but it’s specific
Green tea polyphenols: understudied by consumers, well studied by scientists
Sea buckthorn: less famous, genuinely well backed
The part nobody wants to hear: more antioxidants isn’t automatically better
So does antioxidant skincare actually work?
A quick, honest starting point
Sources referenced in this article

I get asked about antioxidants more than almost anything else. “Is City actually an antioxidant serum or is that just a word you put on the label?” “Do I need vitamin C AND green tea AND resveratrol or is that overkill?” “My old derm said antioxidants don’t do anything, is that true?”

So I did what I always do when I have a question I can’t fully answer from experience alone: I went and read the actual studies. Not the marketing copy other brands write about their own studies. The studies themselves, the peer-reviewed ones, the kind with control groups and boring names like “Journal of Investigative Dermatology.”

Here’s what I found, and where I’ve landed after fourteen years of formulating with this stuff. If you want the broader context first, what climate-adaptive skincare actually means is a good place to start — the antioxidant question is a central part of that story.

What “antioxidant” actually means, biologically speaking

Your skin gets hit with something called reactive oxygen species, or ROS, constantly. UV light generates them. So does pollution, cigarette smoke, and honestly just being alive and metabolizing oxygen. These are unstable molecules missing an electron, and they go around stealing electrons from whatever they bump into: your DNA, your cell membranes, the collagen and elastin holding your skin’s structure together.

This isn’t a vague “toxins” claim. It’s a specific, well-mapped biochemical cascade. When UV radiation hits skin, the resulting flood of ROS activates signaling pathways (MAPK and NF-κB, if you want the actual names) that switch on enzymes called matrix metalloproteinases, or MMPs. MMP-1 in particular is the main collagenase responsible for breaking down type I and III collagen in UV-exposed skin. Researchers reviewing this pathway have described it as UV-induced ROS activating these signaling cascades, which then regulate the genes responsible for producing MMPs, ultimately degrading collagen and elastin (Kim et al., International Journal of Molecular Sciences, 2016). Separately, ROS also inhibit new collagen production by blocking TGF-β signaling, so you’re losing structural protein and losing the ability to rebuild it, at the same time.

Antioxidants work by donating an electron to these unstable molecules before they can go steal one from your skin. That’s it. That’s the whole mechanism. Not magic, not “detoxing,” just chemistry that interrupts a specific, studied pathway.

Where cold climates come in: your skin doesn’t only take this hit from sun. A 2016 review in the Journal of the European Academy of Dermatology and Venereology looked specifically at what happens to skin barrier function in low humidity and low temperature, the exact conditions we deal with here for five or six months a year. The researchers concluded that low humidity and cold temperatures reduce skin barrier function and increase sensitivity to mechanical stress and irritants (Engebretsen et al., 2016). A weakened barrier lets more environmental stress reach living skin cells. So the antioxidant conversation and the “why does my skin fall apart every January” conversation are actually the same conversation — and it’s why transitioning your routine for colder weather is about more than just switching to a heavier moisturiser. That’s a big part of why I formulate the way I do.

Vitamin C: the most researched, and the most misunderstood

Vitamin C (L-ascorbic acid, and its more stable derivatives) is probably the antioxidant with the deepest research base in skincare, and also the one people get the most confused about.

A 2023 systematic review in the Journal of Cosmetic Dermatology looked at randomized controlled trials on topical vitamin C for photoaging and melasma. Every trial that assessed skin texture found that vitamin C-treated skin looked smoother and less wrinkled than the placebo side (Correia et al., 2023). One of the foundational trials behind this, a six-month double-blind study out of France, found that a 5% vitamin C cream produced measurable clinical improvement in photoaged skin compared to the excipient alone, including changes visible at the structural level under the microscope (Humbert et al., Experimental Dermatology, 2003). Beyond the visible stuff, vitamin C has also been shown to inhibit AP-1 activation, which is one of the transcription factors directly responsible for triggering that MMP cascade I mentioned above (reviewed in Al-Niaimi & Chiang, Journal of Clinical and Aesthetic Dermatology, 2017).

So the research holds up. Here’s the part that doesn’t get talked about enough: L-ascorbic acid, the classic “vitamin C serum” form, is genuinely unstable. It needs a very acidic environment (below pH 3.5) to absorb properly, which is exactly why it stings on sensitized skin, and it degrades quickly once exposed to air and light (reviewed in a 2026 systematic review in the same journal). If you’ve ever bought an expensive vitamin C serum, watched it turn orange in the bottle, and wondered if it still worked: it probably didn’t, not as well.

This is the actual reason City uses tetrahexyldecyl ascorbate instead of straight L-ascorbic acid. It’s a more stable, oil-soluble derivative that doesn’t require that harsh low pH to function, which means it doesn’t need to fight your skin barrier to work, and it doesn’t oxidize on your bathroom shelf the same way. I’m not telling you this to sell you City. I’m telling you because if a brand can’t explain why they chose their vitamin C form, that’s worth asking about.

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CITY: Huile antioxydante à la vitamine C

$58.00

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The “combine your antioxidants” research is real, but it’s specific

You’ll see a lot of brands claim their antioxidant blends are “synergistic.” Sometimes that’s true and sometimes it’s a word doing a lot of work it hasn’t earned. The clearest evidence for antioxidant synergy comes from a well-known series of studies out of Duke University. Researchers found that combining vitamin C and vitamin E gave better protection than either alone, because they work in different compartments of the cell (vitamin C in the watery parts, vitamin E in the fatty membranes) and actually regenerate each other after neutralizing a free radical. When they added ferulic acid, a plant-derived antioxidant, to stabilize the mix, they found it didn’t just improve shelf stability. It roughly doubled to quadrupled the skin’s measured protection against UV-simulated damage compared to the vitamin C and E combination alone (Lin et al., Journal of Investigative Dermatology, 2005).

That’s a genuinely impressive result, and it’s the reason “vitamin C + E + ferulic acid” became such a well-known combination in dermatology circles. It’s also a good reminder that antioxidant pairing isn’t just “throw more ingredients in the jar.” City pairs tetrahexyldecyl ascorbate with niacinamide and cranberry seed oil (a natural source of tocopherols, the vitamin E family) for a similar water-and-lipid-phase logic, though I’ll be honest with you: that’s not the identical CEFer formula from the Duke studies, and I’d rather tell you that plainly than let you assume it is.

Green tea polyphenols: understudied by consumers, well studied by scientists

Green tea’s active compound, EGCG (epigallocatechin-3-gallate), has one of the more extensive photoprotection research histories of any plant antioxidant. Early human studies found that applying green tea extract to skin before UV exposure reduced UV-induced redness in a dose-dependent way, with the EGCG and ECG polyphenol fractions being the most effective components tested (Katiyar et al., Journal of the American Academy of Dermatology, 2001). Follow-up research on human skin confirmed that EGCG reduced UVB-induced redness, oxidative stress, and inflammatory cell infiltration (Katiyar, Photochemistry and Photobiology, 2003). A separate placebo-controlled trial in women with moderate photoaging found that combining a 10% green tea cream with oral green tea supplementation over eight weeks led to a significant improvement in elastic tissue quality compared to placebo (Chiu et al., Dermatologic Surgery, 2005).

One detail from a 2012 mechanistic review stood out to me: topical application of EGCG actually outperformed oral green tea consumption for UV protection in the studies that compared both (OyetakinWhite et al., Oxidative Medicine and Cellular Longevity, 2012). Drinking green tea is good for a lot of things. Putting it on your skin appears to matter more for this specific job.

This is one reason green tea shows up across a few different Stark products rather than as a single “hero” serum. Camellia sinensis leaf extract is in Petrichor, Equinox, and Eclipse, and organic green tea seed oil is in Aurora and Boreal. Different parts of the plant, different roles in each formula, but the same underlying antioxidant logic running through the line.

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EQUINOX: Sérum Calme + Lisse

$56.00

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Sea buckthorn: less famous, genuinely well backed

Sea buckthorn (Hippophae rhamnoides) doesn’t get talked about nearly as much as vitamin C, but the research on it is more substantial than most people realize, and it happens to be a cold-climate native plant, which is part of why it’s been in Stark formulas since the beginning.

A 2018 in vitro study exposed human keratinocytes and fibroblasts to UVA and UVB radiation, then treated them with sea buckthorn seed oil. The researchers found the oil partially prevented UV-induced ROS generation and boosted the skin cells’ own antioxidant defenses, including glutathione and vitamins E and A, while also activating Nrf2, a transcription factor that switches on the body’s internal antioxidant enzyme systems (Gęgotek et al., Antioxidants, 2018). That last part matters: sea buckthorn doesn’t just act as an antioxidant itself, it appears to help your skin produce more of its own. Separate research has also connected the oil’s fatty acid profile to genuine regenerative activity in skin cell studies (Dudau et al., Frontiers in Pharmacology, 2021).

Sea buckthorn shows up in Midnight, Deep Midnight, Aurora, and Solstice, usually alongside other barrier-supporting oils and butters. It’s one of the ingredients I’d defend on research grounds alone, not just because it smells good or photographs nicely for Instagram (it does neither, if I’m honest, it’s an odd orange oil that stains everything).

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MIDNIGHT: Sérum d'huile Boost de résilience

$78.00

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AURORA: Baume nettoyant multi-usages

$52.00

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The part nobody wants to hear: more antioxidants isn’t automatically better

Here’s where I’ll push back on the industry a little, including on my own instinct to just add more actives to a formula. Every study I’ve cited above tested a specific ingredient, at a specific concentration, usually in isolation or in a deliberately researched pairing. None of them tested “eight different antioxidant serums layered on top of each other every night,” because nobody would fund that study and the skin barrier probably wouldn’t thank you for it.

The same logic applies here even though antioxidants are gentler by nature than retinol or acids. If you’re layering a vitamin C oil, an antioxidant mist, a green tea toner, and a resveratrol serum all in the same five minutes, you’re not necessarily getting four times the protection. You might just be overloading your skin’s tolerance for actives before it’s even absorbed the first layer, especially if your barrier is already compromised from winter, over-exfoliation, or a rough few months of retinol. Understanding the right order matters too — the guide to skincare layering goes into the logic of what goes where and why.

My actual, unglamorous advice: pick one antioxidant serum as your daytime layer (this is what City is built for, under sunscreen), let a hydrating layer like Equinox do its own job, and let an oil like Midnight handle overnight repair. You don’t need to double up on every category to get the research-backed benefit. This is the subtraction principle again. It shows up everywhere once you start formulating this way.

So does antioxidant skincare actually work?

Based on what’s actually been published, in real trials, on real skin: yes, with real caveats. Vitamin C has the strongest and longest clinical trial history for visible improvements in photoaged skin. Vitamin C, E, and ferulic acid together have measured, published, multiple-fold increases in UV protection over vitamin C alone. Green tea polyphenols have a genuinely deep research base for reducing UV-induced inflammation and oxidative damage, both topically and studied over decades. Sea buckthorn’s fatty acid and antioxidant profile is backed by newer but solid cell-level research, plus a long history of use in the cold-climate regions where it actually grows.

What the research doesn’t support: that you need ten antioxidants at once, that “natural” antioxidants are automatically gentler or more effective than stabilized derivatives, or that any single serum is going to undo a decade of unprotected sun exposure by itself. Antioxidants are a genuinely useful tool for slowing ongoing oxidative damage and supporting your skin’s own defenses. They work alongside daily SPF, not instead of it. Nothing in the research suggests they’re a replacement for it, and I’d rather tell you that than let you think a serum is doing sunscreen’s job.

If you want to actually see this logic in a full routine rather than as a list of ingredients, that’s what the Where Should I Start? quiz walks through, based on your skin’s actual behavior and your actual climate, not just a product list.

A quick, honest starting point

If you’re rebuilding a routine around real antioxidant support rather than marketing claims, here’s roughly where I’d start, and it’s fewer products than you’d think:

Morning, under SPF: City Brightening Antioxidant Serum (tetrahexyldecyl ascorbate + niacinamide) for the vitamin C research above, or Petrichor Antioxidant Mist if your skin runs oilier or more urban-exposed.
Hydration base, any time: Equinox Calm + Smooth Hydration Serum, which also carries green tea leaf extract.
Night, for repair: Midnight Resiliency Boost Oil Serum, for the sea buckthorn research above, or Aurora Cleansing Balm doubled as a leave-on treatment.
Weekly reset: Eclipse Enzyme Facial Cleanser + Mask, which carries green tea extract alongside gentle enzymes, without the acids that would fight your other actives.

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