How to read a peptide serum label

The anatomy of a peptide ingredient name

Cosmetic ingredients are listed by their INCI name, the International Nomenclature of Cosmetic Ingredients. For peptides the name usually has three parts, and once you can read them most labels make sense.

The modification. A prefix tells you what has been attached to the peptide. Palmitoyl and myristoyl mean a fatty acid has been bonded to it; acetyl means an acetyl group has capped one end; copper means the peptide is carrying a copper ion; biotinoyl means biotin is attached. The fatty acid is there for a reason: a laboratory study of the collagen-fragment peptide sold as Matrixyl found that adding palmitic acid is what lets it penetrate skin meaningfully, which is why the cosmetic form carries it ¹. The EU register describes these ingredients in exactly these terms, for example Palmitoyl Tripeptide-1 as the reaction product of palmitic acid and Tripeptide-1, and Copper Tripeptide-1 as a copper complex of Tripeptide-1 ².

The length word. Dipeptide, tripeptide, tetrapeptide, pentapeptide, hexapeptide, octapeptide: two, three, four, five, six or eight amino acids. "Oligopeptide" means a short chain without saying exactly how short.

The number. This is the part people misread. It does not mean stronger, newer or better. It distinguishes peptides that share a length and a modification but have different sequences. Acetyl Hexapeptide-8, Acetyl Hexapeptide-30 and Acetyl Hexapeptide-37 are all six-amino-acid acetylated peptides; by the sequences in our records, the first is Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2 (argireline), the third is Ac-Ser-Pro-Ala-Gly-Gly-Pro-NH2, and the second is a proprietary sequence ³. Three numbers, three unrelated molecules.

How many peptide names there are

We pulled every ingredient name containing "peptide" from CosIng, the European Commission's cosmetic ingredient database, on October 3, 2026. It returned 2,616 names, 1,949 of them with Active status ². The most common prefixes were palmitoyl (190 names), acetyl (164) and myristoyl (45), followed by a long tail of other modifications ². Some names describe recombinant peptides rather than synthetic ones: CosIng describes sh-Oligopeptide-1, for example, as a single-chain recombinant human peptide produced by fermentation in E. coli ².

The functions CosIng records are worth reading carefully. The most frequent were skin conditioning (1,095 names), skin conditioning described as miscellaneous (770), skin protecting (735), antioxidant (447) and hair conditioning (404) ². None of these is "reduces wrinkles" or "grows collagen". They are regulatory categories describing what kind of job an ingredient does in a cosmetic, and listing in CosIng is not an assessment of whether a product works.

The decoder: label name to molecule to evidence

The table below decodes 18 peptide names that appear on serum labels and have entries in our encyclopedia, matched to their CosIng record and to our encyclopedia entries. The last numeric column is a blunt but useful signal: how many PubMed records our October 2026 search found for the ingredient, and how many of those PubMed indexes as randomised controlled trials ⁴. A search match is not a good trial, and some searches catch unrelated uses of a name, so treat the numbers as an upper bound on the evidence, not a measure of it.

A few rows need comment. Argireline appears on labels as both Acetyl Hexapeptide-8 and Acetyl Hexapeptide-3; CosIng lists it as Acetyl Hexapeptide-8 ², and our argireline article covers what its trials found. Palmitoyl Pentapeptide-4 is the peptide sold as Matrixyl, the one with a 93-woman split-face trial in its record ⁵. Copper Tripeptide-1 is GHK-Cu, whose skin evidence our copper peptides guide reviews.

More peptide names you will meet

The 18 names above have encyclopedia entries. Many more appear on labels. The table below decodes 38 further names from their CosIng records, giving the function the register assigns and its own description of what each ingredient is ². Two things stand out. Many descriptions say only that an ingredient is the reaction product of an acid and a numbered peptide, which tells you the modification but not the sequence. And a few names reveal a familiar molecule: CosIng describes Tripeptide-1 as a synthetic peptide containing glycine, histidine and lysine, which is GHK, so Palmitoyl Tripeptide-1, Copper Tripeptide-1 and Nicotinoyl Tripeptide-1 are all the same three amino acids with different attachments ².

What the evidence column tells you

Read down the last numeric column and a pattern is obvious: the names with any trial evidence are the old, famous ones, argireline, Matrixyl and the copper and palmitoyl tripeptides, and most of the rest have a handful of records or none ⁴. Even for the famous ones the trials are small. Argireline's best randomised trial had 60 participants over four weeks ⁶; Matrixyl's split-face trial had 93 women over 12 weeks ⁵. Many of the newer, numbered peptides are known almost entirely from their manufacturers' technical dossiers, which are marketing documents rather than peer-reviewed studies.

That does not make them unsafe or useless. It means the claims on the box, faster collagen, fewer wrinkles, "like Botox", rest on evidence that is mostly unpublished, and the published part is thin. One safety signal is worth knowing: for argireline, the US Cosmetic Ingredient Review panel found the evidence sufficient to call it safe only up to 0.005% in cosmetics ⁷.

How to use this when you shop

Four habits make peptide labels manageable. Read the INCI name, not the marketing name: "peptide complex" on the front of the box is meaningless until you know which peptides are in the list. Do not treat the number as a quality scale: a higher number is a different molecule, not a better one. Look for where the peptide sits in the ingredient list: ingredients are listed roughly in descending order of amount above a threshold, and peptides used at very small concentrations often appear near the end. And check whether the specific peptide has any published human study at all; for most, the answer is no ⁴.

A good peptide serum, in other words, is mostly a good serum: a pleasant, stable formula you will actually use, with a sunscreen in the morning doing far more for ageing skin than any peptide. The peptide is a modest extra whose benefit, for most names on this page, has not been tested in people.

Frequently asked questions

What does palmitoyl tripeptide mean?

A three-amino-acid peptide with palmitic acid, a fatty acid, attached to help it get into skin. Palmitoyl Tripeptide-1, Palmitoyl Tripeptide-5 and Palmitoyl Tripeptide-38 are different peptides; the number distinguishes their sequences.

Is a higher peptide number better?

No. The number tells two peptides of the same length and modification apart. Acetyl Hexapeptide-8, -30 and -37 are unrelated molecules.

How many cosmetic peptides are there?

The EU CosIng database listed 2,616 ingredient names containing 'peptide' when we read it on October 3, 2026, 1,949 of them active.

What is a good peptide serum?

One with a peptide that has at least some published human evidence, such as argireline or palmitoyl pentapeptide-4, in a stable formula you will use, alongside daily sunscreen. Most label peptides have no published randomised trial.

Related on Grey Peptides

• Argireline
• Palmitoyl pentapeptide-4
• Copper peptides for skin

Sources

1. Choi, Y. L., et al. (2014). Dermal Stability and In Vitro Skin Permeation of Collagen Pentapeptides (KTTKS and palmitoyl-KTTKS). Biomol Ther (Seoul), 22(4), 321-7. PMID: 25143811
2. European Commission. CosIng cosmetic ingredient database: all ingredient names containing 'peptide' (2,616 names), read October 3, 2026 through the database's search interface; saved in _ops/phase2/research/cosing_peptides.json. CosIng
3. Grey Peptides dataset: cosmetic peptide entries (sequences and trade names); read October 3, 2026.
4. Grey Peptides evidence counts: PubMed records and records indexed as randomized controlled trials for each entry's search term, read October 3, 2026 (_ops/evidence_counts.json).
5. Robinson, L. R., et al. (2005). Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin. Int J Cosmet Sci, 27(3), 155-60. PMID: 18492182
6. Wang, Y., et al. (2013). The anti-wrinkle efficacy of argireline, a synthetic hexapeptide, in Chinese subjects: a randomized, placebo-controlled study. Am J Clin Dermatol, 14(2), 147-53. PMID: 23417317
7. Johnson, W., Jr., et al. (2025). Safety Assessment of Acetyl Hexapeptide-8 Amide as Used in Cosmetics. Int J Toxicol, 44(2_suppl), 54S-63S. PMID: 40673537

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.