The Vitamin C 23 Serum 20ml
A 20ml ascorbic acid serum for uneven tone and dullness, for morning use by anyone whose skin can take a strong formula.
No reviews yet20 ml
$18.75 per 10 ml
- Korean-market formula
- Ships from California or direct from Korea
- Korean barcode and batch code intact
- Suited to
- Normal skinCombination skinOily skin
- Helps with
- Uneven skin toneSkin that looks dullA daily morning antioxidant step
In stock. Arrives in 3 to 7 business days
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Key benefits
- Ascorbic Acid sits near the top on this product's own ingredient list, a vitamin C derivative included for its brightening, antioxidant role.
- A multifunctional glycol that carries moisture and helps preserve the formula, and Butylene Glycol is right there in this product's ingredient list, near the top.
- On this formula's own list, Panthenol shows up near the top. It is a barrier-supporting provitamin that eases surface roughness.
Key actives
2Ascorbic Acid
The reason the bottle exists, and the ingredient that accounts for both the results people buy it for and the tingle on application.
5Panthenol
A comfort humectant on this list, included so a strong morning serum is a little easier on the skin than it would otherwise be.
63-O-Ethyl Ascorbic Acid
A more stable relative on this list, sitting alongside the pure form, which is an unusual and deliberate pairing in a tone serum.
21Niacinamide
On this list at a position that matters, adding a second angle on tone to a formula already built around the first.
23Glutathione
Present on this list, one of the better established tone ingredients in Korean formulas and a sensible companion here.
Inside the formula
Inside the formula
- 2Ascorbic Acid
- 5Panthenol
- 21Niacinamide
- 23Glutathione
Where each key active sits on the declared ingredient list, by entry number. Position is proportion: the further forward, the larger its share.
Will it sting?
Most people feel a tingle for up to a minute, which is normal for the strong end of this category. Stinging that does not settle is a signal to stop and choose a milder derivative serum instead.
Where does it go in my routine?
In the morning, after the toner and before the moisturizer, with sunscreen as the last layer. The antioxidant side earns its place before a day out, and it sits under sunscreen without trouble. Wait a minute after applying before the next layer goes on.
How long does it keep?
Use it within a few months of opening and keep the bottle closed and out of the light, since this kind of formula does not keep as long as a milder derivative. That is why the bottle is small. If it darkens noticeably, replace it rather than pushing on with it.
Can I use it with a retinoid?
Not in the same sitting. Keep this to mornings and the retinoid to nights, which suits both, since a retinoid is broken down by light anyway. Stacking them together is how people end up flushed and peeling and then abandon both without learning which one suited them.
Is this the Korean-market formula?
Yes. This is the Original Korean Formula 20ml bottle, the same one sold on Korean shelves.
Not on the ingredient list below: fragrance or parfum, denatured or SD alcohol, essential oils, parabens, sulfate surfactants, mineral oil or petrolatum and added color.
Full INCI (30): Aqua/Water, Ascorbic Acid(23%), Butylene Glycol, Dimethicone, Panthenol, 3-O-Ethyl Ascorbic Acid, Squalane, Sodium Hydroxide, Caffeine, Sodium Hyaluronate, Sodium Metaphosphate, Adenosine, Acetyl Glucosamine, Gardenia Florida Fruit Extract, Allantoin, Dextrin, Tocotrienols, Tocopherol, Elaeis Guineensis (Palm) Oil, Arginine, Niacinamide, Pentylene Glycol, Glutathione, Helianthus Annuus (Sunflower) Seed Oil, Methyl Trimethicone, Carthamus Tinctorius (Safflower) Seed Oil, Camellia Japonica Seed Oil, Daucus Carota Sativa (Carrot) Root Extract, Glycyrrhiza Glabra (Licorice) Root Extract, Beta-Carotene
Ingredient list read from jolse.com on 10 September 2026.
30 of 30 explained
- Aqua/Water solvent
- Water is the base almost every serum, toner and cream is built on. It dissolves the water-loving ingredients and sets how light the finished texture feels. On an INCI list it is usually first, which only means it is the largest single ingredient by weight.
- Ascorbic Acid(23%) antioxidant
- Ascorbic Acid is pure vitamin C, the most researched form and also the least stable: it needs a low pH and airtight packaging to stay active. It is an antioxidant used for the look of dullness and uneven tone.
- Butylene Glycol humectant
- Butylene Glycol is a small glycol that does two jobs at once: it holds water in the top layer of skin and it dissolves plant extracts and actives that plain water cannot. It also thins a formula, which is why watery Korean essences lean on it.
- Dimethicone silicone
- Dimethicone is the most used cosmetic silicone. It forms a breathable film that smooths the surface, slows water leaving skin, and gives the slip that makes a primer or cream feel silky. It is inert and does not penetrate.
- Panthenol humectant
- Panthenol is pro-vitamin B5: skin converts it to pantothenic acid. It is a humectant that holds water and leaves skin feeling soft and less tight, and it is one of the ingredients formulators reach for when a formula also contains something harsh.
- 3-O-Ethyl Ascorbic Acid antioxidant
- 3-O-Ethyl Ascorbic Acid is a stable vitamin C derivative that skin converts to ascorbic acid. It survives in a formula far better than pure vitamin C and works at a gentler pH, so it suits skin that finds the pure acid uncomfortable.
- Squalane emollient
- Squalane is the stable, saturated version of squalene, a lipid human skin already makes. It is a light emollient that absorbs quickly, does not oxidise, and is one of the few oils widely considered safe for blemish-prone skin. Most cosmetic squalane is now from sugarcane or olive rather than shark.
- Sodium Hydroxide pH adjuster
- Sodium Hydroxide is a strong base used in traces to bring an acidic formula up to skin-friendly pH. None of it remains as itself once the formula is neutralised.
- Caffeine active
- Caffeine constricts small blood vessels near the surface, which is why eye products use it for the look of puffiness and shadow. It is water soluble and works only while it is on the skin.
- Sodium Hyaluronate humectant
- Sodium Hyaluronate is the salt of hyaluronic acid, and it is what most products labelled hyaluronic actually contain. The salt dissolves more readily and the molecule is smaller, so it sits in the outer layer of skin rather than only on top of it.
- Sodium Metaphosphate chelator
- A phosphate salt that ties up metal ions in water. It also stops the calcium and magnesium in hard water from flattening a cleanser foam.
- Adenosine active
- Adenosine is a nucleoside that Korea's own cosmetic authority recognises as a wrinkle-care functional ingredient, which is why it appears on so many Korean lists at a low level. It is used for the look of fine lines and is stable and well tolerated.
18 more explained
- Acetyl Glucosamine active
- Acetyl Glucosamine is the sugar unit hyaluronic acid is built from. It is used as a humectant and, at higher levels, for the look of uneven tone, often paired with niacinamide.
- Gardenia Florida Fruit Extract plant extract
- Gardenia Fruit Extract is the traditional East Asian yellow dye plant. In skincare it is used as an antioxidant extract, and it can tint a formula.
- Allantoin active
- Allantoin is a comfrey-derived compound used to condition skin and soften the outer layer so it feels smoother. It is one of the standard additions to a formula built for easily irritated skin.
- Dextrin thickener
- Dextrin is a starch fragment used to thicken and to give a formula a light, powdery finish. It is also a common carrier for powdered extracts.
- Tocotrienols antioxidant
- Tocotrienols are the other half of the vitamin E family, usually from rice or palm. They are oil-soluble antioxidants used alongside tocopherol.
- Tocopherol antioxidant
- Tocopherol is vitamin E. It is an oil-soluble antioxidant that protects the oils in a formula from going rancid and works on skin as an emollient, and it is regularly paired with vitamin C because each keeps the other going for longer.
- Elaeis Guineensis (Palm) Oil emollient
- Palm Oil is a rich emollient high in palmitic and oleic acids. In skincare it is more often a source material for esters and emulsifiers than an ingredient on its own.
- Arginine amino acid
- Arginine is an amino acid that does two jobs here: it holds water in the outer layer of skin, and it neutralises acidic gelling agents, which is why it often stands in for a synthetic pH adjuster.
- Niacinamide active
- Niacinamide is vitamin B3, and it is the most studied active in Korean formulation. It is used at roughly 2 to 5 percent for the look of uneven tone and visible pores, and it is water soluble, stable and comfortable beside almost every other active, which is why it turns up in so many lists.
- Pentylene Glycol humectant
- Pentylene Glycol hydrates and, like the other longer-chain glycols, makes a formula less hospitable to microbes so the preservative system can be lighter. It also improves how evenly a product spreads.
- Glutathione antioxidant
- Glutathione is a small peptide the body uses as one of its main antioxidants. In skincare it is used as an antioxidant and for the look of dullness; it is unstable in water, so formulas that carry it are usually built around protecting it.
- Helianthus Annuus (Sunflower) Seed Oil emollient
- Sunflower Seed Oil is high in linoleic acid, the fatty acid dry and blemish-prone skin is often short of. It is a light, non-fragrant emollient and one of the better tolerated plant oils.
- Methyl Trimethicone silicone
- Methyl Trimethicone is a light, volatile silicone chosen for a notably dry finish. It thins a formula and disperses powders evenly.
- Carthamus Tinctorius (Safflower) Seed Oil emollient
- Safflower seed oil, among the highest-linoleic plant oils. High-linoleic oils feel lighter and absorb faster than high-oleic ones.
- Camellia Japonica Seed Oil emollient
- Camellia Seed Oil is the traditional Korean and Japanese hair and skin oil, high in oleic acid. It is a light emollient that absorbs quickly for its richness.
- Daucus Carota Sativa (Carrot) Root Extract plant extract
- Carrot Root Extract carries carotenoids, which give it a strong orange colour. It is used as an antioxidant extract and can tint a formula.
- Glycyrrhiza Glabra (Licorice) Root Extract plant extract
- Licorice Root Extract carries glabridin and liquiritin. It is one of the classic plant ingredients used for the look of uneven tone and redness, and it appears in almost every brightening formula that avoids synthetic actives.
- Beta-Carotene antioxidant
- Beta-Carotene is an orange plant pigment and a vitamin A precursor. It is used as an antioxidant and it tints a formula, which is often why it is there.
- Market
- Korean market, the version sold in Korea
- EAN (barcode)
- 8809598454651
- Made in
- Republic of Korea
- Volume
- 20 ml
- Category
- Serum & Ampoule
- Actives
- Adenosine, Allantoin, Caffeine, Glutathione, Licorice Root, Niacinamide, Panthenol, Sodium Hyaluronate, Squalane, Vitamin C
- Ships from
- California or Korea
Orders ship from California or direct from Korea with tracked delivery to your door, and both routes carry the same Korean-market release. Shipping is free on orders of $100 or more. Returns are accepted for 30 days, by mail.
We split shipments free, so one out-of-stock item never holds up the rest of your order.
Where this unit came from
- 1Seoul
Bought as Korean-market stock - 2Barcode
Listed against the Korean barcode on its box - 3California or Korea
Ships to you from either, as the same Korean-market release
We stock the version of a formula that is sold in Korea, not the release a brand prepares for another market under the same name. The barcode in the specification above is the Korean-market one and it is printed on the box you receive.
Every unit keeps its original barcode and batch code intact, so the unit in your hands can be checked against the brand’s own records.
Every order ships from California or direct from Korea, and returns run for 30 days.
Every claim on this page traces to the unit in the box, the barcode, the batch code and the price you can read for yourself.
How it works
This is the strong end of the tone shelf, and the tingle most people feel on application is the honest signal of that rather than a fault. It is a morning serum, both because the antioxidant side of it earns its place before a day out and because it sits happily under sunscreen. The small bottle is deliberate: an ascorbic acid formula is best used within a few months of opening rather than kept for a year. That is the difference from a milder derivative serum, which is comfortable from day one and keeps longer but works more gradually. What you can judge is whether the face reads clearer and more even in the same light after a month.
How to use
- After cleansing and toning, two or three drops cover the whole face, which is COSRX's own direction.
- Apply after the toner on slightly damp skin, pressing a small amount over the face.
- Wait a minute for the tingle to settle, then apply your moisturizer and finish with sunscreen.
- Do not use it in the same sitting as an exfoliating product or a retinoid, and keep the bottle closed and out of the light.
Worth knowing
- Expect a tingle on application, and stop if it turns into stinging that does not settle within a minute.
- Sensitive skin should choose a milder derivative serum instead of starting here.
- Use it within a few months of opening and keep it closed and away from light.
Complete the routine
- This itemCOSRX The Vitamin C 23 Serum 20ml$37.50
- Seal the routine in as the last stepCOSRX Skin Barrier Moisturizing Cream 450ml$42.50
- An as-needed step, in place of the prep layerCosrx 5 PDRN Hyaluronic Acid Vital Hydrating Hydrogel Mask$4.70
Total for 3 items$84.70
Reviews
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COSRX The Vitamin C 23 Serum 20ml
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COSRX, Korean-market original
A 20ml ascorbic acid serum for dull, uneven looking skin, stocked in the Original Korean Formula.
Verify your unit when it arrives
Verify your unit when it arrives
Korean-market stock with the original barcode and batch code intact, exactly as it left Korea.
COSRX verifies units itself. Find the verification page on cosrx.com and enter the batch number and expiration date printed on your unit. Read them off the package rather than from us, which is the point.
Source: COSRX FAQ
On the unit itself
- The Korean-market barcode, unaltered from the retail package.
- The manufacturer’s batch code, exactly as the maker printed it.
정품Genuine article, Korean-market stock
What professionals say
What professionals say
What skin-care professionals say about the key actives in this formula, quoted from the medical sources linked beside each.
Using topical vitamin C can result in less cell damage and better-looking skin.
Melissa Piliang, MDDermatologist, Cleveland Clinic Pantothenol is a common ingredient in skin care and hair products I recommend, particularly for people who are prone to dryness.
Taylor Bullock, MDDermatology resident, Cleveland Clinic
1 more professional perspective
Niacinamide helps reduce the appearance of pores in a few ways. By strengthening the skin barrier and improving elasticity, pores appear less noticeable and more even.
Ashlyn YankeAesthetician, Cleveland Clinic
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