Peptides in Skincare: What They Are and How to Use Them

Peptides have travelled from the biochemistry textbook straight onto the K-beauty shelf: serums, boosters, eye creams and masks now compete on how many peptides they pack, and the word sits in the name of every other launch. With the hype comes one very practical question: how do you even recognise a peptide on an ingredient list?

The answer is on the back of the box, in the INCI list: a peptide shows up as the word "peptide" inside an ingredient name, and the prefix in front of it tells you how long the chain is.

The examples come from Korean brands we know well: Medicube, COSRX and Mary&May. The full line-up is in our peptides collection.

What peptides are, in plain words

Peptides are short fragments of proteins: chains of a few amino acids linked in a row. Picture a protein as a whole wall — a peptide is a handful of bricks joined together. That short chain length is what separates peptides from full proteins, and it is what their entire role in skincare is built on.

The prefix in the name tells you the chain length: a dipeptide has two amino acids, a tripeptide three, a hexapeptide six; an oligopeptide is a short chain and a polypeptide a long one. When a box says "Tripeptide" or "Hexapeptide", that is not marketing poetry — it is chemical nomenclature.

Peptides and collagen: how they relate

The easiest way to understand the fuss about peptides is through collagen. The CosIng register describes collagen as a fibrous protein comprising a third of all protein in mammals — and, in the register's own words, "a polypeptide containing three peptide chains". In other words, collagen itself is built out of peptide chains. Peptides and collagen are not rivals; they are chapters of the same story about skin firmness.

Which is why they so often turn up side by side in the same product. Mary&May's Collagen Peptide Vital Mask combines low-molecular collagen with six peptides — a pairing the brand describes as care aimed at wrinkles and elasticity. There is more on collagen itself in our collagen guide and in the collagen collection.

What the EU CosIng register says about peptides

CosIng, the European Commission's database of cosmetic ingredients, is very dry on peptides. For the three we checked, the register lists one or two functions apiece and not a single promise:

Not a word about wrinkles, lifting or "Botox effects": the register logs only an ingredient's basic function. Everything more specific — firmness, glow, fine lines — comes from manufacturers' descriptions, and that is exactly how we present it in this article: as brand claims.

Copper Tripeptide-1: the common thread across Korean brands

If one peptide ties Korean brands together, it is the copper peptide Copper Tripeptide-1 — a tripeptide paired with copper, as the name itself says. In our selection it appears in the ingredient lists of all three brands: Medicube's serums and eye cream, COSRX's peptide booster, and Mary&May's collagen mask.

Per CosIng its function is skin conditioning — anything beyond that is brand copy. But the mere fact that the same peptide runs through the catalogues of three different manufacturers says plenty about how much of an industry standard it has become in Korea.

Palmitoyl peptides and other frequent INCI groups

The second big family is the palmitoyl peptides — peptides with a palmitic (fatty) acid residue attached, hence the "Palmitoyl" in the name. Palmitoyl Pentapeptide-4 and Palmitoyl Tripeptide-1 appear at both Medicube and Mary&May; Medicube also formulates with Palmitoyl Tetrapeptide-7 and Palmitoyl Hexapeptide-12.

Then there is Acetyl Hexapeptide-8 — found in the COSRX booster and in all three Medicube products in this guide, and, of the three peptides we checked in CosIng, the only one the register lists as a humectant — a moisture-binding ingredient — alongside skin conditioning.

How to read an ingredient list and spot the peptides

A few practical rules for when you flip the box over:

  • look for the word "peptide" inside INCI names — Copper Tripeptide-1, Palmitoyl Pentapeptide-4, Acetyl Hexapeptide-8;
  • the prefix gives the chain length: di- (2), tri- (3), tetra- (4), penta- (5), hexa- (6), nona- (9), with oligo- and poly- for shorter and longer chains;
  • the number after the dash identifies a specific amino-acid sequence — it is neither a quantity nor a "strength" rating;
  • check front-of-pack claims ("6 Peptide", "Multi Peptide") against the INCI list — that is where the real formula lives.

In fairness, none of the three brands publishes a peptide percentage on its official product page. Where the manufacturer gives no number, neither do we.

Counting peptides: six, six and thirteen

Peptide skincare has spawned a whole genre — counting the peptides in a formula. COSRX says its The 6 Peptide Skin Booster Serum "blends six powerful peptides" to address fine lines, uneven texture and loss of firmness. Mary&May describes its mask as "composed of six peptides mixed in a golden ratio". Both brands publish the number themselves.

Medicube does not advertise a count — but in the official ingredient list of the Hyaluronic Multi Peptide Serum (listed on the brand's page as Hyaluronic Multi Peptide PDRN Serum) we counted thirteen peptide INCI names: from Dipeptide-2 and Tripeptide-1 through Copper Tripeptide-1 to Nonapeptide-1 and Oligopeptide-1. That is our observation from the published list, not a brand claim — but it is quite a list.

Peptides vs retinol: the gentler road to firmness

Say "firmness" and most people think of retinol first — we cover it in a separate retinol guide, introduction rules and all. A peptide routine is a different, softer road: the usage instructions for the peptide products in this guide contain no gradual acclimatisation schedule. Medicube's directions for its PDRN Pink serum are simply: apply morning and night to clean skin.

If you lean towards the gentle side, it also helps that the COSRX booster is, per the brand, clinically tested for irritation (including on sensitive skin) and non-comedogenic, with hydration and firmness results tested independently by the Dermacosmetic Skin Science Laboratory — all wording from the official product page.

Nor is it an either-or choice: Medicube's eye cream lists PDRN, retinol, peptides and niacinamide together among its key ingredients — and claims its 99%-purity retinol "effectively boosts skin elasticity around eye area". Peptides and retinol evidently share a jar just fine.

Peptides + PDRN: the Korean pairing

If one ingredient defines recent Korean skincare, it is PDRN, an ingredient with a PDRN guide of its own. Medicube built an entire pink line on the PDRN + peptides pairing: the PDRN Pink Peptide Serum carries five peptides alongside Rose PDRN, and the brand describes it as care for glow, even tone and skin elasticity.

The same peptide quintet — Copper Tripeptide-1, Acetyl Hexapeptide-8 and three palmitoyl peptides — travels to the eye area in the PDRN Pink Peptide Eye Cream. And in the big thirteen-peptide serum they sit next to Salmon DNA PDRN, which the brand links to care for uneven tone and dark spots. The PDRN collection brings together every product with this ingredient.

Peptides as step one: a booster in the toner slot

We are used to actives living in a serum, somewhere mid-routine. COSRX moved peptides to the very start: by the brand's instructions, The 6 Peptide Skin Booster Serum is used "after cleansing as a toner before ampoule, serum or moisturizer". A few drops, patted in gently — then carry on as usual.

The appeal of the format is that the peptide step changes nothing else in your routine — it simply slots in ahead of it. If you have been torn between a toner and yet another serum, the booster settles the argument.

Peptides as the last step: the eye cream

At the opposite end of the routine sits the eye cream. Medicube's directions for the PDRN Pink Peptide Eye Cream open with "as the last step of your skincare routine": apply an appropriate amount to the desired area and pat lightly for better absorption. The brand promises a healthier, more youthful look for the eye area through care for wrinkles and fine lines — its wording, of course.

So within a single routine peptides can be both the opening line and the closing note: booster before everything, eye cream after everything. More for that zone is in the eye creams collection.

Peptides in sheet masks

The third format is the mask. Mary&May's Collagen Peptide Vital Mask is a sheet mask with six peptides "in a golden ratio" plus low-molecular collagen; the brand frames the combination as wrinkle-and-elasticity care and adds adenosine — an ingredient that, per the brand's description, supports collagen production in the skin.

The instructions are simple: after cleansing and toner, the mask stays on for 10–15 minutes, then the remaining essence is massaged lightly into the skin, avoiding the eye and lip areas. A peptide step in the shape of a quarter-hour pause.

How to fit peptides into your routine

Stack the brands' instructions together and a peptide routine looks like this:

  • Cleansing — every peptide story starts on clean skin.
  • Peptide booster or toner — COSRX: a few drops right after cleansing, patted in.
  • Serum — Medicube advises shaking its multi-peptide serum before use so the oil layer and serum layer mix, then patting it in; the PDRN Pink serum goes on morning and night, face and neck.
  • Moisturiser — seals in the steps before it.
  • Eye cream — per Medicube's instructions, the last step of the routine.

Add a mask as an occasional ritual, following the manufacturer's directions. And you do not need everything at once: starting with a single product and building from there is a perfectly good plan.

Who peptides make sense for

A peptide routine is a logical pick if you want your skincare aimed at firmness and elasticity but strong actives do not appeal; if you enjoy layered Korean routines — peptides now exist at every step, from booster to eye cream; and if you prefer products their brands describe as irritation-tested, like the COSRX booster.

If you are pregnant, breastfeeding or managing a skin condition, talk to your doctor or dermatologist before introducing any new cosmetic ingredient. And our whole peptide line-up is waiting in the peptides collection.

If one habit is worth taking away, it is turning the box over. A number on the front sounds convincing, but only the INCI list shows which peptides are actually in the formula, and on what they do the CosIng register is far more modest than the brands. Where peptides end up in your routine, as a booster at the start or an eye cream at the end, depends on the product you pick.

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