Cosrx Advanced The Vitamin C 23 Serum
A morning vitamin C serum for a brighter, more even look, in a 20 g bottle, for skin already comfortable with a daily vitamin C step.
No reviews yet- Ships from our California warehouse
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- Suited to
- NormalOilyCombinationNot recommended as a first vitamin C serum for sensitive or reactive skin
- Helps with
- Pronounced dullnessDark spots and hyperpigmentationSkin already comfortable with vitamin C wanting a stronger dose
In stock. Ships from our California warehouse, dispatched within 2 business days
You’re $100.00 away from free US shipping.
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- 30-day returns
- Free US shipping on orders of $100 or more
- Dispatched within 2 business days
How it works
This is the vitamin C step in a morning routine, in COSRX's 20 g size. It goes on after toner, on dry skin, and before moisturizer and sunscreen. What it works on is tone: a brighter, more even look that builds over weeks of daily mornings rather than in a single application. Skin new to a vitamin C serum usually does better starting every other morning and building up from there. It suits someone who already has a cleanser, a toner and a sunscreen in place and wants one active step between them.
Key benefits
- Ascorbic acid is declared at 23 percent, second on the list right after water
- 3-O-ethyl ascorbic acid at six is a second, more stable vitamin C form working alongside the primary one
- Tocotrienols at seventeen, a stronger antioxidant vitamin E form, and glutathione at twenty-three support and extend the vitamin C's effect
- Squalane and three plant oils toward the end of the list offset the dryness a high-percentage vitamin C can leave behind
- Niacinamide at twenty-one adds a fourth brightening mechanism to an already dense stack
- No fragrance, no parfum, no essential oil on the list
Key actives
Ascorbic AcidDeclared at 23 percent, second on the list
One of the highest declared ascorbic acid concentrations in the store's catalog. Pure ascorbic acid is the most studied vitamin C form and the most likely to cause initial sensitivity, which is why this serum is positioned for skin already comfortable with vitamin C.
3-O-Ethyl Ascorbic AcidA second, more stable vitamin C form at position six
Less prone to oxidation than pure ascorbic acid, it extends the serum's brightening effect and helps the formula hold its potency longer once opened.
TocotrienolsA vitamin E form with a stronger antioxidant profile than standard tocopherol, at seventeen
COSRX markets this as super vitamin E for its more potent antioxidant activity, included specifically to work alongside the ascorbic acid rather than as a standalone claim.
GlutathioneAn antioxidant tripeptide positioned at twenty-three
Works alongside the vitamin C and vitamin E as a third antioxidant layer, a combination frequently used together in high-strength brightening formulas.
What is the COSRX Vitamin C 23 Serum for?
It is a high-strength brightening serum for pronounced dullness and dark spots, built on ascorbic acid declared at 23 percent, second on the list. A second vitamin C form, tocotrienols and glutathione work alongside it to extend and support the effect, for skin already comfortable with vitamin C rather than as a first one to try.
Is 23 percent too strong for my skin?
It can be, especially if you have not used vitamin C before or your skin runs sensitive. This concentration is built for people already comfortable with lower-strength vitamin C serums who want a stronger dose. Patch test first.
Will it cause dryness or irritation?
High-percentage ascorbic acid can be drying or mildly irritating on some skin, which is why squalane and three plant oils sit further down the list to offset that. Starting every other day rather than daily is a common way to build tolerance.
Can I use this with a retinoid or exfoliating acid?
Most people alternate a high-strength vitamin C serum with a retinoid or acid rather than layering them the same session, since combining several strong actives at once raises irritation risk. AM for vitamin C, PM for a retinoid is a common split.
How does this compare to buying COSRX from a US retailer?
COSRX verifies units itself. Find the verification page on cosrx.com and enter the batch number and expiration date printed on your unit, read off the package rather than from us, which is the point. 8800311121256, and batch code intact under the box.
- Ships from
- California
Duties are prepaid. Nothing is owed at delivery. Returns are accepted for 30 days, by mail.
Orders ship from our California warehouse, dispatched within 2 business days, and arrive in 3 to 5 days. Shipping is free on orders of $100 or more.
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 - 2Customs
Duty paid by us before it enters the US - 3California
Ships domestically, no international leg
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.
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.
Import duties are paid by us before the parcel reaches you, so nothing is owed at the door, 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.
Payment and security
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How to use
- AM, after toner, as a brightening step. Start every other day if you are new to vitamin C at this strength.
- A few drops pressed evenly over the face, avoiding the eye area where skin is thinner and more reactive.
- Let it fully absorb, several minutes if needed, before layering anything else on top.
- Follow with moisturizer and sunscreen without fail, since vitamin C works best paired with daily sun protection.
Worth knowing
- This is a 23 percent ascorbic acid serum, one of the most concentrated vitamin C formulas in our catalog. If you have not used vitamin C before, start with a lower-percentage serum first.
- Ascorbic acid at this concentration can sting on compromised, freshly exfoliated or very sensitive skin. Patch test before applying to the full face.
- Sodium hydroxide is present to adjust pH for the ascorbic acid's stability, not as a treatment ingredient.
Reviews
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Korean-market original
The Vitamin C 23 Serum, 20 g, 23% ascorbic acid second on the list.
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.
Match the batch code on the box against the code printed on the bottle or tube itself; the two are stamped separately and should agree.
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 skin care, 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 Pretty much every step of a Korean skin care routine is going to have some component of hydration.
Alok Vij, MDDermatologist, Cleveland Clinic
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