What Are Peptides in Skincare?

One skincare peptide started as a five-amino-acid piece of a molecule your body uses to make collagen, and in lab tests that piece prompted skin cells to make more collagen.² Peptides are short chains of amino acids, the same small molecules that make up proteins.¹ In skincare they're studied for several jobs. Some can influence how much collagen skin cells make, while others bind copper or act on the chemical signals behind facial movement.^{2, 4, 5} Which job a peptide does depends partly on the order of its amino acids. Whether it does that job on your face is another matter, and that depends on the formula around it and on what studies in people show.

How does a short peptide affect collagen?

Collagen is a protein that helps support skin, and cells called fibroblasts, the skin's collagen makers, build it by joining amino acids into long chains. Researchers have studied how much collagen fibroblasts produce when they're exposed to certain short peptides.² The collagen fragment is one of them. Called KTTKS, it's a chain of five amino acids, which makes it a pentapeptide, and in experiments with cells grown in a lab it prompted them to make more collagen and another supporting protein called fibronectin.² There's a nice logic to it, with a piece of the body's own collagen-making material nudging cells to make more.

That makes KTTKS a signaling peptide, meaning a peptide that influences what a cell does. It works a bit like a note left for a factory crew, telling the workers to make more.

Skincare uses a modified version. Attaching a fatty-acid group to KTTKS creates the ingredient Palmitoyl Pentapeptide-4, and researchers tested a moisturizer containing it against the same moisturizer without it, with each woman in the study using the two on opposite sides of her face. The moisturizer with the peptide produced greater improvement in fine lines and wrinkles.³ The cell experiments explain why researchers looked at the peptide in the first place, and the moisturizer study is where they checked for visible change on skin.

Some peptides do more than one job

GHK is a chain of three amino acids, a tripeptide, and it can bind copper ions, which are electrically charged forms of copper. Together, the peptide and copper are called GHK-Cu, and peptides that bind a metal this way are commonly called carrier peptides.^{4, 9} GHK-Cu has also prompted fibroblasts grown in a lab to make more collagen, so it fits both descriptions, binding copper and acting as a signal that changes what cells do.⁴ The copper peptide guide goes into it in more detail.

What about peptides for expression lines?

Another line of research looks at the chemical messages involved in facial movement. Releasing those messages requires a group of proteins to join together, a little like a zipper that has to close before anything goes out. Acetyl Hexapeptide-8, also known as Argireline, was designed around part of one of those proteins, and in laboratory experiments it disrupted how the group formed or stayed together. It's a clever target. Researchers have studied whether disrupting the group could help soften expression lines.^{5, 6}

Studies in people have disagreed, and the two studies are easier to read once you see what each compared. One compared an Argireline preparation with a placebo preparation that didn't contain it, and found improvement in lines around the eyes with Argireline.⁶ The other compared a hyaluronic-acid serum with and without Argireline on opposite sides of the face, and didn't establish an added wrinkle benefit from the peptide.⁷

There's also the question of whether Argireline gets where it would need to be. For its proposed effect on nerve signals, it would have to reach the cells involved, and how well it does is still an open question. In a laboratory experiment with human skin, most of the Argireline, applied in a mixture of water and oil, stayed on the surface, and none was detected in the dermis, a deeper layer of skin.⁸ For a peptide meant to work below the surface, that's a lot of it staying on top.

Why does the formula matter?

Dissolving a peptide in a formula is one step, and helping it move from the formula into skin is another. GHK-Cu dissolves in water, which gives formulators a way to include it in a product. An emulsion combines water and oil, with small droplets of one spread through the other the way fat droplets are spread through milk, and many creams are emulsions, so water-soluble ingredients and oils can share a product.⁹

Researchers tested how different emulsions affected the delivery of Argireline into pig skin. The water-rich mixtures delivered the peptide into skin more effectively than the oil-rich mixture tested alongside them.¹⁰ The peptide was the same in every version, so the difference came from the formula around it.

How to read a peptide on a label

With GHK-Cu, each term now points to something specific. "Carrier" describes its ability to bind copper, "signaling" describes its effects on cells, and the fact that it dissolves in water helps explain how it fits into a formula. You can read any peptide you come across the same way. Its name identifies the ingredient, its role explains why it's being studied, and its formula affects whether it's delivered. Studies in people then tell you about visible results, for the particular product that was tested.

For water-soluble peptides, we see a formula containing water as a useful starting point. That's why we've left peptides out of Omnia, our waterless lipid formula, and plan to include them in future water-based products.

For product formats, ingredient names and percentages, see how to choose and use a peptide serum. The skincare peptide reference covers individual ingredients.

Sources

1. International Union of Pure and Applied Chemistry. Peptides. Compendium of Chemical Terminology, 5th ed., 2025.
2. Katayama K, et al. A pentapeptide from type I procollagen promotes extracellular matrix production. Journal of Biological Chemistry, 1993.
3. Robinson LR, et al. Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin. International Journal of Cosmetic Science, 2005.
4. Maquart FX, et al. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+. FEBS Letters, 1988.
5. Blanes-Mira C, et al. A synthetic hexapeptide (Argireline) with antiwrinkle activity. International Journal of Cosmetic Science, 2002.
6. Wang Y, et al. The anti-wrinkle efficacy of argireline, a synthetic hexapeptide, in Chinese subjects: a randomized, placebo-controlled study. American Journal of Clinical Dermatology, 2013.
7. Henseler H. Investigating the effects of Argireline in a skin serum containing hyaluronic acids on skin surface wrinkles using the Visia® Complexion Analysis camera system for objective skin analysis. GMS Interdisciplinary Plastic and Reconstructive Surgery DGPW, 2023.
8. Kraeling MEK, et al. In vitro skin penetration of acetyl hexapeptide-8 from a cosmetic formulation. Cutaneous and Ocular Toxicology, 2015.
9. Badenhorst T, et al. Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal delivery. Pharmaceutical Development and Technology, 2016.
10. Hoppel M, et al. Topical delivery of acetyl hexapeptide-8 from different emulsions: influence of emulsion composition and internal structure. European Journal of Pharmaceutical Sciences, 2015.