Peptides are short protein fragments; collagen itself, by the CosIng registry's description, is a polypeptide built of three peptide chains. In Korean skincare peptides are the firmness step, and the ingredient list shows exactly which ones you get: Copper Tripeptide-1 appears in COSRX, Medicube and Mary&May formulas alike, usually alongside palmitoyl peptides.
Counting peptides has become the category's signature. COSRX blends six of them in a booster for fine lines and loss of firmness and, unusually, places it at the very start of a routine — used after cleansing, like a toner. Mary&May also builds its daily sheet mask on six peptides in what the brand calls a golden ratio, plus adenosine, which by the brand's description supports collagen production. Medicube goes furthest: the composition of its multi-peptide serum lists thirteen peptide INCI names next to salmon PDRN, and its eye cream combines peptides with 99%-purity retinol as the final step of a routine.
Peptides slot into any step — a booster after cleansing, a serum in the middle, an eye cream at the end, a 10–15-minute mask a few times a week — and they pair comfortably with hydrators such as hyaluronic acid.
Choosing a first peptide product, go by zone: an all-face serum for overall firmness, an eye cream for the lines around the eyes.
What peptides are, how to read them in an INCI list and where they fit in a routine — in our peptide guide.
