Peptide Skincare Ingredient Decoder
You're standing in a store, flipping a serum bottle around, and the ingredient list reads: "Palmitoyl Tripeptide-1, Acetyl Hexapeptide-8, Copper Tripeptide-1." If you don't speak cosmetic chemistry, those look like random words and numbers.
You're standing in a store, flipping a serum bottle around, and the ingredient list reads: "Palmitoyl Tripeptide-1, Acetyl Hexapeptide-8, Copper Tripeptide-1." If you don't speak cosmetic chemistry, those look like random words and numbers.
They're not. Every part of a peptide INCI name tells you something specific about what the ingredient is, how it was modified, and how many amino acids it contains. Once you understand the naming convention, you can decode any peptide label in seconds.
This guide is a translation key. It takes the INCI names you see on product labels and tells you what they actually mean, what each peptide does, and how they connect to the trade names (Matrixyl, Argireline, Eyeseryl) you've probably heard of.
Table of Contents
- How INCI Names Work
- Decoding Peptide Names: The Three-Part System
- Common Peptide INCI Names and What They Are
- Trade Names vs. INCI Names: The Rosetta Stone
- Prefixes Explained in Detail
- Spotting Peptides on Product Labels
- What the Ingredient Position Tells You
- Common Confusions and Pitfalls
- Frequently Asked Questions
- The Bottom Line
- References
How INCI Names Work
INCI stands for International Nomenclature of Cosmetic Ingredients. It's a global standardized naming system developed by the Personal Care Products Council (PCPC) that ensures every cosmetic ingredient has a consistent, unambiguous name -- regardless of brand, country, or language [1].
INCI names appear on the ingredient lists of every cosmetic product sold in the US, EU, and most other regulated markets. They're listed in descending order of concentration (with a caveat: below 1%, ingredients can be listed in any order the manufacturer chooses) [1].
You'll never see trade names like "Matrixyl" or "Argireline" on an ingredient list. Those are marketing names owned by the companies that developed those peptides. On the actual label, you'll see the INCI name: Palmitoyl Pentapeptide-4 for Matrixyl, Acetyl Hexapeptide-8 for Argireline.
This is why knowing how to decode INCI names matters. It cuts through the marketing and tells you exactly what's in the product.
Decoding Peptide Names: The Three-Part System
Most cosmetic peptide INCI names follow a consistent three-part structure:
[Prefix] + [Peptide Type] + [-Number]
Example: Palmitoyl Tripeptide-1
- Palmitoyl = prefix (palmitic acid modification)
- Tripeptide = peptide type (3 amino acids)
- -1 = registry number (first tripeptide registered with this modification)
Let's break down each part.
Part 1: The Prefix (Chemical Modification)
The prefix tells you what chemical modification was made to the peptide. These modifications are not random -- they're carefully engineered to improve the peptide's stability, skin penetration, or biological activity [2].
| Prefix | What It Means | Why It's There |
|---|---|---|
| Palmitoyl | Palmitic acid (C16 fatty acid) chain attached | Increases lipophilicity for better skin penetration through the lipid-rich stratum corneum |
| Acetyl | Acetyl group (CH3CO-) attached to the N-terminus | Improves stability and penetration; protects against enzymatic degradation |
| Copper | Copper(II) ion complexed with the peptide | Provides copper for enzymatic cofactor activity (lysyl oxidase, SOD) |
| Myristoyl | Myristic acid (C14 fatty acid) chain attached | Similar to palmitoyl; improves skin penetration |
| Hexanoyl | Hexanoic acid (C6) chain attached | Shorter lipid modification for improved penetration |
| Stearyl/Stearoyl | Stearic acid (C18) chain attached | Lipid modification for penetration and stability |
| No prefix | Unmodified peptide | Native sequence; may rely on other delivery methods |
The most common prefix you'll encounter is palmitoyl. Palmitic acid is the most abundant fatty acid in human skin. Attaching it to a peptide creates a molecule that the stratum corneum recognizes as somewhat "familiar," facilitating passage through the lipid barrier [2].
Acetyl is the second most common prefix. The acetyl group caps the peptide's N-terminus, protecting it from aminopeptidases (enzymes that break down peptides starting from the amino end). This extends the peptide's half-life on the skin, giving it more time to penetrate and act [2].
Part 2: The Peptide Type (Chain Length)
This tells you how many amino acids are in the chain:
| Term | Number of Amino Acids | Example |
|---|---|---|
| Dipeptide | 2 | Dipeptide Diaminobutyroyl Benzylamide Diacetate |
| Tripeptide | 3 | Copper Tripeptide-1 (GHK-Cu) |
| Tetrapeptide | 4 | Acetyl Tetrapeptide-5 (Eyeseryl) |
| Pentapeptide | 5 | Palmitoyl Pentapeptide-4 (Matrixyl) |
| Hexapeptide | 6 | Acetyl Hexapeptide-8 (Argireline) |
| Heptapeptide | 7 | Copper Palmitoyl Heptapeptide-14 |
| Octapeptide | 8 | Acetyl Octapeptide-3 (Snap-8) |
| Nonapeptide | 9 | Nonapeptide-1 |
| Oligopeptide | Multiple (typically >6) | Palmitoyl Oligopeptide |
Smaller peptides (di-, tri-, tetrapeptides) generally penetrate skin more easily due to their lower molecular weight. Larger peptides (hexa-, octa-) may require more sophisticated delivery systems [3].
Part 3: The Number (Registry Identifier)
The number after the hyphen is a unique identifier assigned by the PCPC registry. It distinguishes different peptides of the same chain length and modification.
For example:
- Palmitoyl Tripeptide**-1** is a different peptide from Palmitoyl Tripeptide**-5** -- they both have three amino acids with a palmitoyl modification, but the actual amino acid sequences are different, giving them different biological activities.
- Tripeptide**-1** without a prefix is different from Palmitoyl Tripeptide**-1** -- the same amino acid sequence, but one has the fatty acid modification and one doesn't.
The number itself doesn't indicate quality, potency, or when the peptide was developed. It's simply a catalog number.
Common Peptide INCI Names and What They Are
Here's a comprehensive decoder for the peptides you're most likely to encounter on product labels:
Signal Peptides (Collagen Stimulators)
| INCI Name | Trade Name | What It Does |
|---|---|---|
| Palmitoyl Pentapeptide-4 | Matrixyl | Stimulates collagen I, III, IV, fibronectin, and HA synthesis |
| Palmitoyl Tripeptide-1 | Part of Matrixyl 3000 / Biopeptide CL | Collagen fragment mimicry; stimulates matrix protein production |
| Palmitoyl Tetrapeptide-7 | Part of Matrixyl 3000 / Biopeptide EL | Anti-inflammatory; reduces inflammaging-driven collagen loss |
| Palmitoyl Tripeptide-38 | Matrixyl Synthe'6 | Stimulates 6 ECM components simultaneously |
| Palmitoyl Tripeptide-5 | Syn-Coll | Activates TGF-β for collagen production |
| Copper Tripeptide-1 | GHK-Cu | Collagen remodeling + copper delivery (signal + carrier) |
| Tripeptide-29 | Collagen Peptide | Mimics the Gly-Pro-Hyp collagen repeat sequence |
Neurotransmitter-Inhibiting Peptides (Expression Line Reducers)
| INCI Name | Trade Name | What It Does |
|---|---|---|
| Acetyl Hexapeptide-8 | Argireline | SNARE complex inhibition; reduces muscle contraction |
| Acetyl Octapeptide-3 | Snap-8 | Extended Argireline; ~30% more active |
| Pentapeptide-18 | Leuphasyl | Enkephalin receptor agonist; reduces ACh secretion |
| Dipeptide Diaminobutyroyl Benzylamide Diacetate | Syn-Ake | Nicotinic ACh receptor antagonist (viper venom-inspired) |
| Acetyl Hexapeptide-3 | Argireline (older name) | Same as Acetyl Hexapeptide-8 (name was updated) |
| Tripeptide-3 | Syn-Ake (alternative listing) | Same compound, alternate INCI registration |
Eye-Area Peptides
| INCI Name | Trade Name | What It Does |
|---|---|---|
| Acetyl Tetrapeptide-5 | Eyeseryl | ACE inhibition; reduces puffiness and dark circles |
Carrier Peptides
| INCI Name | Trade Name | What It Does |
|---|---|---|
| Copper Tripeptide-1 | GHK-Cu | Delivers copper for enzymatic activity; tissue remodeling |
| Copper Palmitoyl Heptapeptide-14 | N/A | Copper delivery with lipid modification |
| Manganese Tripeptide-1 | N/A | Delivers manganese for MnSOD antioxidant support |
Sensitivity and Barrier Peptides
| INCI Name | Trade Name | What It Does |
|---|---|---|
| Palmitoyl Tripeptide-8 | Neutrazen | Calms neurogenic inflammation; reduces sensitivity |
| Acetyl Tetrapeptide-15 | Skinasensyl | Reduces pain receptor sensitivity |
| Acetyl Dipeptide-1 Cetyl Ester | Calmosensine | Calms irritation; anti-sensitivity |
Trade Names vs. INCI Names: The Rosetta Stone
Here's a critical point: trade names never appear on ingredient lists. They're marketing names used in product descriptions, advertising, and brand communication. On the actual product label (the legal ingredient declaration), you'll only see INCI names [1].
Sometimes a single trade name covers multiple INCI ingredients:
Matrixyl 3000 = Glycerin + Water + Butylene Glycol + Carbomer + Polysorbate 20 + Palmitoyl Tripeptide-1 + Palmitoyl Tetrapeptide-7
The trade name "Matrixyl 3000" refers to the entire commercial ingredient blend, which includes the two active peptides plus various carrier and stabilizer ingredients. On the label, you'll see each component listed separately according to INCI rules.
Haloxyl = N-Hydroxysuccinimide + Chrysin + Palmitoyl Tripeptide-1 + Palmitoyl Tetrapeptide-7
Notice that Haloxyl and Matrixyl 3000 share the same two peptides (Palmitoyl Tripeptide-1 and Palmitoyl Tetrapeptide-7) but differ in the non-peptide components. On a label, you can't tell whether the manufacturer used "Matrixyl 3000" or "Haloxyl" (or both) just by reading the INCI names -- you'd need the brand to specify.
Prefixes Explained in Detail
Palmitoyl
By far the most important prefix in cosmetic peptide chemistry. Palmitic acid (hexadecanoic acid, C16:0) is a 16-carbon saturated fatty acid -- the most abundant fatty acid in the human body and a major component of the skin's lipid barrier [2].
When you attach palmitic acid to a peptide, you get a palmitoylated peptide that:
- Crosses the stratum corneum more easily (the lipid barrier "recognizes" the fatty acid portion)
- Is more resistant to enzymatic degradation (the lipid chain protects the peptide bond)
- Has improved stability in cosmetic formulations
- Can partition into both oil and water phases of emulsion products
This modification is so effective that most modern signal peptides are palmitoylated. The unmodified KTTKS sequence (the basis of Matrixyl) has poor skin penetration. Adding the palmitoyl chain (creating Pal-KTTKS) transforms it into a practical skincare ingredient [4].
Acetyl
An acetyl group (CH3CO-) attached to the peptide's N-terminus. This modification:
- Protects against aminopeptidases (enzymes that attack the amino end of peptides)
- Improves stability in aqueous solutions
- May improve skin penetration modestly (less than palmitoylation)
- Is the preferred modification for neurotransmitter-inhibiting peptides
Most of the expression-line peptides use acetyl modification rather than palmitoyl. This may be because their targets (SNARE complex proteins, acetylcholine receptors) are at the neuromuscular junction, which is accessible from the aqueous compartment of the dermis. Heavy lipid modification might actually slow their delivery to the target.
Copper
Not a chemical modification in the same sense as palmitoyl or acetyl. "Copper" in a peptide INCI name indicates that a copper(II) ion is complexed with the peptide through coordinate bonds -- typically involving histidine and lysine residues in the peptide sequence [5].
The copper is an active component, not a modifier. GHK-Cu's biological activity depends on the copper ion for enzymatic cofactor function (lysyl oxidase, superoxide dismutase) and for triggering specific gene expression patterns.
Products containing copper peptides have a characteristic blue color from the copper(II) ion. Colorless products claiming copper peptide content either have negligible concentrations or are using an improperly complexed form.
Spotting Peptides on Product Labels
When reading an ingredient list, look for these telltale patterns:
Any word ending in "-peptide-" followed by a number is a peptide ingredient. Examples: Tripeptide-1, Hexapeptide-8, Oligopeptide-68.
Words with "palmitoyl," "acetyl," or "copper" followed by a chain-length term are modified peptides. Examples: Palmitoyl Pentapeptide-4, Acetyl Hexapeptide-8, Copper Tripeptide-1.
"Hydrolyzed collagen" is not a signaling peptide. It's a protein hydrolysate used as a moisturizing ingredient. It can improve skin hydration and feel, but it doesn't trigger the fibroblast signaling that signal peptides produce. The collagen fragments are typically too large and too heterogeneous to bind specific receptors [6].
"Silk amino acids" or "soy protein hydrolysate" are not the same as defined peptide sequences. These are bulk hydrolysates containing a mixture of peptide fragments. Some may have enzyme-inhibiting activity, but they're not the precisely engineered peptides referenced in clinical studies.
What the Ingredient Position Tells You
INCI rules require ingredients above 1% concentration to be listed in descending order. Below 1%, ingredients can appear in any order [1].
For peptides, this creates ambiguity. Most active peptides work well below 1% (Matrixyl shows effects at 3 ppm, which is 0.0003%). So a peptide listed near the bottom of the ingredient list isn't necessarily at a sub-therapeutic level -- it might be at the perfect concentration.
However, if a peptide appears dead last on a very long list -- after fragrance, colorants, and preservatives that are typically present at 0.01-0.5% -- it could be present at levels too low to matter. This is sometimes called "fairy dusting" or "label dressing": adding a tiny amount of a trendy ingredient to justify a marketing claim.
Practical guidelines:
- Peptide in the top third of the list = definitely present at meaningful levels
- Peptide in the middle third = likely at working concentrations
- Peptide at the very bottom, after fragrance and colorants = possibly sub-therapeutic; check if the brand discloses actual concentrations
For a broader understanding of what makes peptide products effective, see our complete guide to peptides in skincare and our peptide serums ingredient analysis.
Common Confusions and Pitfalls
Confusion: "Peptide Complex" without INCI disclosure. Some brands list "Proprietary Peptide Complex" in marketing materials but don't specify which peptides on the actual label. Every ingredient must have an INCI name on the product -- check the ingredient declaration, not the marketing copy.
Confusion: Same peptide, different names. Argireline has been registered under multiple INCI names over time: Acetyl Hexapeptide-3 (older) and Acetyl Hexapeptide-8 (current). They're the same molecule. Similarly, Syn-Ake may appear as either Dipeptide Diaminobutyroyl Benzylamide Diacetate or Tripeptide-3.
Confusion: Trade name ingredients on the label. You might see "Matrixyl" in marketing but "Palmitoyl Pentapeptide-4" on the label. They're the same thing. You might also see the carrier ingredients from the Matrixyl commercial blend (glycerin, butylene glycol, carbomer, polysorbate 20) listed separately -- these are the non-peptide components of the commercial ingredient.
Confusion: Numbers don't indicate generation or potency. Tripeptide-1 is not "better" or "newer" than Tripeptide-5. The number is an arbitrary registry identifier, not a quality ranking. Palmitoyl Pentapeptide-4 has more evidence than Palmitoyl Pentapeptide-17 -- the number doesn't predict anything about the ingredient's performance.
Pitfall: Assuming all peptides do the same thing. A product listing six different peptides sounds impressive, but if they're all signal peptides, you're getting six variations of the same mechanism. A product with three peptides from different categories (one signal, one neurotransmitter-inhibiting, one enzyme-inhibiting) may be more effective.
For guidance on how to layer peptide products with other actives, see our dedicated guide.
Frequently Asked Questions
Can I tell a product's quality just from reading the INCI list? You can tell which peptides are present and roughly whether they're at meaningful concentrations. You can't tell the exact concentration, the delivery system quality, the pH, or the stability of the formulation from the INCI list alone. But it's a powerful starting point -- it eliminates products that don't contain the peptides they claim to and helps you compare products objectively.
Why do some products list peptides I've never heard of? New peptide sequences are regularly registered with the PCPC and assigned INCI names. Some are from emerging research; others are from manufacturers creating proprietary peptides for their exclusive use. Not having a familiar name doesn't mean a peptide is bad -- but it does mean you should check whether any published research supports its claims.
What does "Oligopeptide" mean on a label? "Oligo-" means "few" or "several." An oligopeptide contains multiple amino acids (typically more than six) without specifying an exact count. It's a more generic term than "hexapeptide" (exactly 6) or "octapeptide" (exactly 8). Some ingredients use "oligopeptide" when the exact amino acid count isn't specified in the registration.
Is "hydrolyzed collagen" the same as a collagen peptide? Not in the way that matters for anti-aging signaling. Hydrolyzed collagen is a mixture of collagen fragments of various sizes produced by breaking down collagen protein. Signal peptides like Matrixyl are precisely defined amino acid sequences designed to bind specific receptors. Hydrolyzed collagen moisturizes the skin surface. Signal peptides communicate with fibroblasts to stimulate new collagen production. Different mechanisms, different outcomes.
How do I know which peptide category an ingredient belongs to? You need to cross-reference the INCI name with its known mechanism. This guide's decoder tables above do this for the most common peptides. For less common peptides, check the manufacturer's technical documentation or published research.
The Bottom Line
Peptide INCI names aren't random strings of chemical jargon. They're a code that tells you exactly what's in a product: which amino acid chain, which chemical modification, and which specific peptide sequence. Learning to read this code takes five minutes and pays off every time you evaluate a skincare product.
The three-part system -- prefix (modification) + peptide type (chain length) + number (registry ID) -- decodes any peptide name. Know that palmitoyl means better penetration, acetyl means better stability, and copper means mineral delivery. Know that the number is just a catalog identifier, not a quality ranking. Know that trade names (Matrixyl, Argireline) are marketing and INCI names are what actually appears on labels.
Armed with this knowledge, you can cut through marketing claims and evaluate peptide products based on what they actually contain. That's the difference between informed skincare and expensive guesswork.
References
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Personal Care Products Council. "INCI Nomenclature Conventions." 2023. PCPC
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Gorouhi F, Maibach HI. "Role of topical peptides in preventing or treating aged skin." Int J Cosmet Sci. 2009;31(5):327-345. PubMed
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Bos JD, Meinardi MM. "The 500 Dalton rule for the skin penetration." Exp Dermatol. 2000;9(3):165-169.
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Katayama K, et al. "A pentapeptide from type I procollagen promotes extracellular matrix production." J Biol Chem. 1993;268(14):9941-4.
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Pickart L, et al. "GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration." BioMed Research International. 2015;2015:648108. PMC4508379
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Apostolopoulos V, et al. "Peptides: Emerging Candidates for the Prevention and Treatment of Skin Senescence." Biomolecules. 2025;15(1):88. PMC11762834