A two-ingredient antioxidant serum that does something no other product in your routine can: regenerate itself after neutralizing free radicals. It won't dazzle you with visible overnight results, but EUK 134 is quietly one of the most sophisticated — and absurdly affordable — protective serums available.
EUK 134 0.1%
A two-ingredient antioxidant serum that does something no other product in your routine can: regenerate itself after neutralizing free radicals. It won't dazzle you with visible overnight results, but EUK 134 is quietly one of the most sophisticated — and absurdly affordable — protective serums available.
Score Breakdown
A genuinely innovative antioxidant mechanism at an exceptional price point, but the ultra-minimal formulation means you are paying almost exclusively for one active — which works brilliantly for some routines but offers no additional skincare benefits beyond antioxidant protection.
Data Confidence: medium
This product has been available since 2017, but it remains a niche offering within The Ordinary's lineup with approximately 300-400 reviews across platforms. The underlying EUK 134 compound has peer-reviewed research supporting its antioxidant mechanism, but real-world cosmetic validation is more limited than The Ordinary's bestsellers.
0/100
Overall Score
Ingredient Quality 0
Value for Money 0
Suitability Breadth 0
Irritation Risk (↑ = safer) 0
Assessment
Pros
- Self-regenerating antioxidant mechanism that no other consumer skincare product offers
- Only two ingredients — virtually zero risk of irritation or allergic reaction
- Exceptionally affordable at $11.50 for a genuinely novel active ingredient
- Backed by peer-reviewed research demonstrating UV-protective and anti-inflammatory effects
- Works for all skin types including rosacea-prone and highly reactive skin
- Effective even when applied after UV exposure, not just before
- Fragrance-free, oil-free, silicone-free, vegan, and fungal acne safe
- Pairs well with retinoids, niacinamide, and hyaluronic acid
Cons
- Six-month shelf life is shorter than most serums and may lead to waste
- Benefits are primarily preventative and invisible — no dramatic cosmetic results
- Incompatible with vitamin C suspensions, azelaic acid, and copper peptides
- Oily-feeling texture on application takes 1-2 minutes to fully absorb
- Only available in one size with no option for a smaller trial bottle
Full Review
There is a particular kind of product that skincare obsessives find irresistible: one that sounds like it was borrowed from a biochemistry lab, does something genuinely novel, and costs less than lunch. The Ordinary's EUK 134 0.1% is that product. And the fact that it has remained one of the brand's quietest offerings since its 2017 launch tells you something interesting about the gap between what sounds exciting and what actually is.
EUK 134 — formally, ethylbisiminomethylguaiacol manganese chloride — is a synthetic salen-manganese complex. If that means nothing to you, here is the translation that matters: it mimics two of your body's most important antioxidant enzymes, superoxide dismutase and catalase. The first converts superoxide free radicals into hydrogen peroxide. The second converts that hydrogen peroxide into water and oxygen. Your body does this naturally, but environmental stress, UV exposure, and aging degrade these enzymes over time. EUK 134 picks up where your biology leaves off.
What makes this genuinely different from every vitamin C, vitamin E, and ferulic acid serum on your shelf is a single property: self-regeneration. Traditional antioxidants are sacrificial. They neutralize a free radical, and in doing so, they are consumed. Gone. EUK 134 resets. After each antioxidant reaction, the manganese complex returns to its original state and goes again. It is, in the most literal sense, a recyclable antioxidant.
The formula itself is almost aggressively simple. Two ingredients. Propanediol — a corn-derived glycol that acts as the vehicle — and the EUK 134 complex at 0.1%, which DECIEM notes is more than double the typical suggested use level. There are no supporting players, no peptide cameos, no hyaluronic acid in the chorus. This is a one-act show.
On the skin, it feels like a lightweight facial oil despite being technically oil-free. The golden-amber liquid has a silky slip courtesy of the propanediol, and it takes a minute or two to absorb fully. If you are the type of person who dislikes any residual slip between steps, patting rather than rubbing will speed things along. Once it settles, the finish is smooth and barely perceptible under moisturizer.
The question most people ask about EUK 134 — does it actually do anything? — reveals a fundamental misunderstanding of how preventative skincare works. You will not wake up with visibly brighter skin. You will not see your pores shrink. What you will get, over weeks and months, is a layer of enzymatic protection that neutralizes oxidative damage before it has the chance to become the hyperpigmentation, fine lines, and dullness you will notice three years from now. Published research supports this: a 2004 study in the International Journal of Cosmetic Science showed that EUK 134 reduced lipid peroxides on UV-exposed skin in vivo, and — unusually — was effective even when applied after UV exposure, not just before it. A separate study in the Journal of Investigative Dermatology the same year demonstrated that EUK 134 pre-treatment significantly improved cell survival following UVB exposure and inhibited stress-activated signaling pathways.
That said, some users do report a visible benefit that shows up relatively quickly: reduced redness. If your skin tends toward a baseline flush — not full rosacea, but that general pinkness that never quite calms down — EUK 134 seems to take the edge off within two to four weeks. The mechanism makes sense: oxidative stress is a significant driver of skin inflammation, and neutralizing it at the enzymatic level addresses the cause rather than masking the symptom.
The trade-offs are worth naming honestly. The six-month shelf life is notably short, especially for a serum that does not deliver dramatic visible results — it requires a certain faith in the science to keep repurchasing something that works invisibly. The incompatibility list is longer than average, too. You cannot layer this with L-ascorbic acid suspensions, azelaic acid suspensions, copper peptides, or strong direct acids, because acidic environments destroy the manganese complex. This means building a routine around EUK 134 requires some scheduling — alternating AM and PM, or dedicating certain days to certain actives. For minimalist routine builders, this is a non-issue. For twelve-step maximalists, it demands compromises.
At $11.50 for 30 mL, the value proposition is remarkable. There is no other product on the market at any price that offers a self-regenerating SOD and catalase mimetic for daily use. The technology was developed by Lucas Meyer Cosmetics and has legitimate research behind it — this is not a marketing story dressed up as science. Whether you are using this as your primary antioxidant or as a complement to vitamin C in a separate routine, the cost of entry is negligible.
The Ordinary EUK 134 0.1% is the skincare equivalent of wearing a seatbelt. It will never be the most exciting part of your routine. You will never post about it. But it is doing something genuinely useful in the background, protecting your skin through a mechanism that no other consumer product replicates. And it does it for the price of a mediocre cocktail.
Formula
Ingredients
The hero actives that drive this product's performance.
| Ingredient | Function | Evidence |
|---|---|---|
| EUK 134 (Ethylbisiminomethylguaiacol Manganese Chloride) (0.1%) | A synthetic salen-manganese complex that mimics both superoxide dismutase and catalase — the body's two primary antioxidant enzymes. Unlike conventional antioxidants that get consumed upon neutralizing a free radical, EUK 134 regenerates itself after each reaction, providing continuous protection. In this ultra-minimal two-ingredient formula, it works without interference from other actives, maximizing its ability to convert reactive oxygen species into harmless water and oxygen. | promising |
| Propanediol | A corn-derived glycol that serves as the sole vehicle for the EUK 134 active. Beyond simply dissolving the complex, propanediol provides mild humectant properties and a smooth slip that helps the product spread evenly, ensuring uniform antioxidant distribution across the skin without the need for water or additional solvents. | well-established |
Full INCI List
Propanediol, Ethylbisiminomethylguaiacol Manganese Chloride
Product Flags
✓ Fragrance Free✓ Alcohol Free✓ Oil Free✓ Silicone Free✓ Paraben Free✓ Sulfate Free✓ Cruelty Free✓ Vegan✓ Fungal Acne Safe
Compatibility
Skin Match
Best For
Works For
Not Ideal For
Addresses These Conditions
sun damage aging dullness sensitivity compromised skin barrier
Routine Step
serum
Time of Day
AM & PM
Pregnancy Safe
Yes ✓
Layering Tips
Apply a few drops after water-based serums and before oils or moisturizers. Can also be mixed into a moisturizer. Avoid layering with direct acids, L-ascorbic acid suspensions, or copper peptides in the same routine.
Results Timeline
Immediate: smooth, slightly dewy feel from the propanediol base. 2-4 weeks: some users notice reduced redness and improved skin tone. Long-term (8+ weeks): cumulative antioxidant protection manifests as more even skin tone and better resilience against environmental stressors. Benefits are primarily preventative — protecting against future damage rather than correcting existing concerns.
Pairs Well With
NiacinamideHyaluronic AcidRetinoidsNon-copper peptidesSunscreen
Conflicts With
L-Ascorbic Acid (pure suspensions)Azelaic Acid SuspensionCopper PeptidesStrong direct acids at high concentrations
Sample AM Routine
- Gentle cleanser
- Hyaluronic Acid serum
- The Ordinary EUK 134 0.1%
- Moisturizer
- Sunscreen SPF 30+
Sample PM Routine
- Gentle cleanser
- Niacinamide serum
- The Ordinary EUK 134 0.1%
- Moisturizer
Evidence
Science
The Science
EUK 134 belongs to a class of compounds called salen-manganese complexes, synthetic molecules designed to mimic the activity of antioxidant metalloenzymes. Its dual function as both a superoxide dismutase (SOD) and catalase mimetic is what sets it apart from conventional antioxidants that typically target only one step of the reactive oxygen species cascade.
The most relevant dermatological study comes from Decraene et al., published in the Journal of Investigative Dermatology in 2004. The researchers applied EUK 134 to primary human keratinocytes before UVB exposure and found that it significantly reduced p53 accumulation — a marker of DNA damage — and inhibited activation of the mitogen-activated protein kinase (MAPK) signaling pathways that drive inflammation and photoaging. Cell survival was markedly improved compared to untreated controls.
A companion study by Declercq et al. in the International Journal of Cosmetic Science (2004) tested EUK 134 in an in vivo setting on human skin. The researchers measured hydroperoxide levels — indicators of lipid peroxidation — on UVA-exposed skin and found that EUK 134 reduced these levels significantly. Notably, EUK 134 was effective when applied both before and after UV exposure, while alpha-tocopherol (vitamin E) only worked as a pre-treatment. This post-exposure efficacy suggests EUK 134 can address oxidative damage that has already been initiated, not just prevent its onset.
The self-regenerating property is the compound's most distinctive feature from a pharmacological standpoint. Traditional antioxidants like L-ascorbic acid and tocopherol donate electrons to neutralize free radicals and are oxidized in the process — they become spent. EUK 134's manganese center cycles between oxidation states, returning to its catalytically active form after each reaction. This catalytic cycling means a small amount of the compound can neutralize a disproportionately large number of free radicals over time, which helps explain why the 0.1% concentration — while seemingly low — is actually more than double the manufacturer's suggested use level.
References
- A Synthetic Superoxide Dismutase/Catalase Mimetic (EUK-134) Inhibits Membrane-Damage-Induced Activation of Mitogen-Activated Protein Kinase Pathways and Reduces p53 Accumulation in Ultraviolet B-Exposed Primary Human Keratinocytes — Journal of Investigative Dermatology (2004)
- Use of the synthetic superoxide dismutase/catalase mimetic EUK-134 to compensate for seasonal antioxidant deficiency by reducing pre-existing lipid peroxides at the human skin surface — International Journal of Cosmetic Science (2004)
Dermatologist Perspective
Dermatologists recognize EUK 134 as a scientifically interesting antioxidant with a mechanism distinct from the more commonly recommended vitamin C and E. Board-certified dermatologists note that the dual SOD and catalase mimicry addresses multiple steps of the oxidative stress cascade, which is pharmacologically elegant. The ultra-minimal formulation makes it a useful recommendation for patients with contact dermatitis histories, multiple chemical sensitivities, or skin that reacts to seemingly everything — there are simply no common sensitizers present. Dermatologists typically recommend pairing it with broad-spectrum sunscreen for maximum photoprotective benefit, as antioxidants and UV filters work synergistically. It is not a replacement for sunscreen, but rather an additional layer of defense against the oxidative damage that UV filters alone cannot fully prevent.
Guidance
Usage Guide
How to Use
Apply 3-4 drops to clean, dry skin after water-based serums and before oils or moisturizers. Pat gently into the face and neck — rubbing is unnecessary and may slow absorption. Can be used morning and evening, though morning application maximizes its UV-protective benefits when paired with sunscreen. Alternatively, mix a few drops into your moisturizer for a simplified application. Allow 1-2 minutes for absorption before layering the next step. Do not combine with L-ascorbic acid, azelaic acid suspensions, or copper peptide products in the same routine.
Value Assessment
At $11.50 for 30 mL, The Ordinary EUK 134 0.1% offers extraordinary value for a genuinely novel active ingredient. There is no comparable self-regenerating SOD/catalase mimetic available at any price point in the consumer skincare market. The only size available means no volume discount, but the low base price and 4-6 month lifespan per bottle make the annual cost under $30 for daily antioxidant protection. For budget-conscious skincare enthusiasts who want evidence-backed antioxidant coverage without the instability and higher cost of vitamin C serums, this is one of the most compelling value propositions in The Ordinary's entire lineup.
Who Should Buy
Anyone seeking a no-fuss, budget-friendly antioxidant that works through a mechanism entirely different from vitamin C or E. Particularly valuable for sensitive skin types who react to most serums, and for those who want to add a layer of enzymatic UV protection beyond sunscreen alone.
Who Should Skip
If you want visible, rapid results — brighter skin, faded dark spots, smoother texture — this product works too subtly and too slowly to satisfy. Also not ideal if your routine is built around L-ascorbic acid or copper peptides, as the incompatibilities require restructuring your entire regimen around one $11.50 serum.
Ready to try The Ordinary EUK 134 0.1%?
Details
Details
Texture
A lightweight, oil-like liquid with a slight golden-amber tint. Despite the oily initial feel, it absorbs within a couple of minutes to a smooth, non-greasy finish. Based on propanediol rather than actual oils.
Scent
No discernible scent
Packaging
Amber glass dropper bottle with The Ordinary's standard minimalist white label and black text. The dark glass helps protect the light-sensitive EUK 134 complex from degradation.
Finish
lightweightdewynon-greasy
What to Expect on First Use
On first application, the product feels like a lightweight facial oil despite being oil-free. There is no tingling, stinging, or adjustment period. Results are subtle and cumulative — do not expect visible changes in the first few days. Some users notice reduced redness within the first two weeks.
How Long It Lasts
4-6 months with once-daily application of 3-4 drops to the face
Period After Opening
6 months
Best Season
All Year
Certifications
VeganCruelty-Free
Background
The Why
DECIEM introduced EUK 134 in 2017 as part of The Ordinary's expanding antioxidant lineup, aiming to offer a fundamentally different approach to free radical protection. The ingredient itself was developed by Lucas Meyer Cosmetics in Canada and is based on salen-manganese chemistry originally studied for neuroprotective applications. It remains one of The Ordinary's least-discussed but most scientifically interesting products.
About The Ordinary Established Brand (5–20 years)
The Ordinary launched under DECIEM in 2016 and rapidly became the most disruptive force in skincare by offering clinical-grade actives at unprecedented price points. Now owned by Estée Lauder Companies, the brand has built nearly a decade of consumer trust through ingredient transparency and accessible pricing.
Brand founded: 2016 · Product launched: 2017
Myth vs. Reality
Myths
Myth
EUK 134 is just another vitamin C alternative
Reality
EUK 134 works through an entirely different mechanism than vitamin C. It mimics enzymes (SOD and catalase) rather than acting as a direct radical scavenger, and unlike vitamin C, it self-regenerates after each antioxidant reaction. The two are complementary but not interchangeable — though they should not be used in the same routine due to pH incompatibility.
Myth
You can't see any results, so it must not be working
Reality
EUK 134's primary function is preventative — protecting against oxidative damage before it becomes visible. Published research shows it reduces lipid peroxides and inhibits UV-induced cellular stress. The absence of dramatic visible changes is by design; it's protecting against damage you would otherwise accumulate over years.
FAQ
FAQ
What does The Ordinary EUK 134 0.1% actually do?
EUK 134 is a synthetic antioxidant that mimics two of your body's own protective enzymes — superoxide dismutase and catalase. It neutralizes free radicals caused by UV exposure and pollution, then regenerates itself to keep working. The benefits are primarily preventative: it protects against cumulative oxidative damage rather than correcting existing concerns.
Can I use EUK 134 with vitamin C?
Not in the same routine. EUK 134's manganese complex is destabilized by strong acids, including L-ascorbic acid suspensions. However, you can use vitamin C in the morning and EUK 134 at night, or alternate days. Vitamin C derivatives like ascorbyl glucoside may be better tolerated alongside EUK 134, but The Ordinary recommends separating them.
Is EUK 134 better than vitamin C for antioxidant protection?
They work differently. Vitamin C is a direct radical scavenger that also boosts collagen synthesis and brightens skin, but it degrades after use. EUK 134 regenerates itself after each reaction, providing continuous protection — but it lacks vitamin C's collagen and brightening benefits. Many dermatologists view them as complementary rather than competing, used in separate routines.
Why does The Ordinary EUK 134 feel oily?
The product's base is propanediol, a corn-derived glycol with an oil-like slip. It is technically oil-free, silicone-free, and non-comedogenic. The slightly oily feel on application is the vehicle, not actual oils. It absorbs within 1-2 minutes and leaves a smooth, non-greasy finish.
How long does The Ordinary EUK 134 last once opened?
The Ordinary gives this product a 6-month Period After Opening (PAO), which is shorter than most serums. The manganese complex can degrade over time, especially if exposed to light or strong acids. With once-daily use of 3-4 drops, the 30 mL bottle should last 4-6 months — aligning with the PAO window.
Can I use EUK 134 with retinol?
Yes. EUK 134 pairs well with retinoids including retinol, granactive retinoid, and retinal. The antioxidant protection from EUK 134 can actually complement retinoid use by neutralizing some of the oxidative stress that retinoids can generate. Apply EUK 134 before or after your retinoid in the PM routine.
Is The Ordinary EUK 134 safe for sensitive skin?
This is one of the safest products for sensitive skin on the market. With only two ingredients — propanediol and the EUK 134 complex — there are no fragrances, preservatives, surfactants, or common irritants. It is free of every major allergen category. Users with rosacea and eczema-prone skin frequently report good tolerance.
Community
Community
Common Praise
"Noticeably reduces facial redness within weeks of consistent use"
"Ultra-minimal ingredient list is ideal for reactive and sensitive skin"
"Self-regenerating antioxidant is scientifically more efficient than vitamin C or E"
"Exceptional value at $11.50 for a unique, research-backed active"
"Layers well under moisturizer once absorbed"
Common Complaints
"Oily-feeling texture requires patience for absorption"
"Preventative benefits are difficult to see or measure day-to-day"
"6-month shelf life is short — some users cannot finish the bottle"
"Incompatible with many popular actives, limiting routine flexibility"
Appears In
best serum for sensitive skin best antioxidant serum best the ordinary products best serum for redness best budget antioxidant
Related Conditions
sun damage aging dullness sensitivity compromised skin barrier
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