Peptides are short chains of amino acids. In skincare, they are a large family of ingredients, each with its own INCI name, purpose and level of evidence. Most are classified as skin-conditioning. Much of the research behind them comes from suppliers or laboratory studies, so read peptide claims as claims about specific ingredients, not the whole family.
What a peptide is
Amino acids link together to form chains. Long chains are proteins, such as collagen and keratin. Short chains, typically a few to a few dozen amino acids, are peptides. Cosmetic peptides are usually made synthetically and often modified, for example with a palmitoyl or acetyl group, which changes how they behave in a formula.
Why the full name matters
The number in a name like Tetrapeptide-5 or Hexapeptide-11 is an identifier in the naming system. “Tetra” and “hexa” tell you there are four or six amino acids, but two tetrapeptides can be entirely different. Acetyl Tetrapeptide-5 and Palmitoyl Tetrapeptide-7 are different ingredients with different claims.
Groups you’ll hear about
Ingredient writers often sort cosmetic peptides into loose groups:
- “Signal” peptides, such as Palmitoyl Pentapeptide-4 and Palmitoyl Tripeptide-1, often marketed for firmness and lines.
- “Neurotransmitter-inhibiting” peptides, such as Acetyl Hexapeptide-8, often marketed for expression lines.
- “Carrier” peptides and copper complexes, such as Copper Tripeptide-1 (GHK-Cu). What copper peptides are.
- Peptides marketed for specific areas, such as Acetyl Tetrapeptide-5 for the eye area.
These groupings describe what the ingredients are marketed for. They aren’t proof of results.
What the evidence looks like
- A lot of peptide research is supplier-funded, uses small groups, or is done in the lab rather than on people.
- Results for one peptide at one concentration don’t transfer to another peptide, or to a product with an undisclosed amount.
- Getting ingredients into the skin is a real challenge, which is one reason modified forms exist.
- Cosmetics are regulated for appearance. Claims that a product changes skin structure are drug-like claims.
That doesn’t make peptides useless. It means the honest description of most peptide products is “contains X, which is claimed to Y,” not “does Y.”
How to read a peptide claim
- Which peptide? Find the INCI name.
- How much? A “10% peptide complex” is usually a supplier blend that is mostly water or glycerin, not 10% peptide. What a percentage tells you.
- Whose evidence? A supplier study, an independent study, or none?
- Which result? Is the claim about appearance (cosmetic) or about changing the skin (drug-like)?
Peptides in our formulas
- 001 Copper Peptide Cream: Copper Lysinate/Prolinate (an amino acid–copper complex). Guide.
- 002 Peptide Eye Gel: Acetyl Tetrapeptide-5. Guide.
- 003 Retinol Night Serum: Hexapeptide-11, alongside retinol. Guide.
We name each one, label supplier claims as supplier claims, and don’t publish percentages we haven’t had verified. Our editorial standards.
Further reading: INCIDecoder: Acetyl Tetrapeptide-5 · INCIDecoder: Hexapeptide-11 · FDA: Wrinkle treatments and other anti-aging products
Explore the ingredients in our four formulas.
Photography: 360floralflaves / Unsplash. Editorial photograph.