The Steinder Weisen Peptide Guide (Version 1)

The Steinder Weisen Peptide Guide is a plain-language, evidence-rated guide to the peptides used in anti-aging skincare. It explains what each common skincare peptide is, what it is meant to do for your skin, and how strong the scientific evidence behind it really is, from well-studied ingredients such as Matrixyl (Palmitoyl Pentapeptide-4), copper peptide (GHK-Cu) and Argireline (Acetyl Hexapeptide-8) to newer peptides whose research is still emerging.

This is Version 1 of the guide, published in October 2026. Peptide science is moving quickly, and new studies, supplier data and our own formulation testing will keep changing what we know. We will continue to review the research, update our evidence ratings and release new versions of this guide as we gather more data. When a rating changes, we will say so and explain why. If there is a peptide you have seen on a label and want explained, tell us and we will consider it for the next version.

We wrote this guide because peptides have become one of the most heavily marketed ingredient categories in anti-aging skincare, and also one of the least understood. Ingredient labels list names like Palmitoyl Tripeptide-38 or Dipeptide Diaminobutyroyl Benzylamide Diacetate with no explanation, and the front of the box often promises more than the research supports. Some peptides have decades of laboratory and clinical research behind them. Others have a single study run by the company that sells them, or none at all in human skin. We believe you deserve to know the difference, in the same spirit as the ingredient dictionaries that first brought honest, cited ingredient ratings to skincare shoppers.

What are peptides in skincare?

Peptides are short chains of amino acids. Amino acids are the building blocks the body uses to make proteins, including collagen and elastin, the two proteins most responsible for keeping skin firm, smooth and springy. When amino acids link together in long chains, they form proteins. When only a few are linked, usually between two and about fifty, the result is called a peptide. A “tripeptide” has three amino acids, a “pentapeptide” has five and a “hexapeptide” has six, which is why those words appear so often on ingredient labels.

In skincare, peptides are designed to act as messengers. Many of them copy small fragments of the skin’s own proteins. When collagen naturally breaks down, it leaves behind fragments, and the skin appears to read those fragments as a sign that repair is needed. A peptide that mimics one of those fragments may prompt skin cells to produce more collagen and other supporting proteins. Other peptides work as carriers, delivering trace minerals such as copper that the skin’s repair enzymes need. Still others aim to soften the muscle signaling behind expression lines. The word “palmitoyl” at the start of many peptide names means that a fatty acid chain has been attached to the peptide to help it travel through the skin’s oily outer layers.

How we rate the evidence

Every peptide in this guide is given one of four evidence ratings, based on how well it has been tested on human skin rather than how impressive it looks in a laboratory. A peptide rated Strong has published, controlled studies in human skin, ideally from more than one independent research group. A peptide rated Moderate has some human studies, which are often small, short or funded by the company that makes the ingredient, supported by solid laboratory research. A peptide rated Emerging has mostly laboratory or cell-culture research, with limited or no published data from human skin. A peptide rated Unproven has little published research beyond the supplier’s own claims.

A lower rating does not mean an ingredient does nothing. It means the evidence has not yet caught up with the claims, and that you should keep your expectations in proportion. It is also worth knowing that, as of this version, no cosmetic peptide fully meets our Strong rating. Even the best-studied peptides rest on fewer and smaller studies than proven skincare ingredients such as retinoids and sunscreen. Ratings in this guide may move up or down in future versions as new research is published.

What are the four types of skincare peptides?

Cosmetic scientists usually sort skincare peptides into four groups according to how they are meant to work. Signal peptides are the largest group. They mimic fragments of broken-down collagen or other skin proteins, and the idea is that they prompt skin cells to produce more collagen and more of the extracellular matrix, the supportive network that gives skin its structure. Palmitoyl Pentapeptide-4, Palmitoyl Tripeptide-1, Palmitoyl Tripeptide-5 and Palmitoyl Tripeptide-38 are all signal peptides.

Carrier peptides deliver trace minerals that the skin needs for repair. The best-known example is Copper Tripeptide-1, usually called GHK-Cu or copper peptide, which carries copper to the enzymes involved in building collagen and healing skin. Neurotransmitter-inhibitor peptides aim to soften the muscle signaling behind expression lines such as frown lines and crow’s feet, and are often marketed as “Botox-like.” Acetyl Hexapeptide-8, sold as Argireline, and Dipeptide Diaminobutyroyl Benzylamide Diacetate, sold as Syn-Ake, belong to this group, although their effects are much milder than injectable treatments. Enzyme-inhibitor peptides aim to slow down the enzymes that break collagen down; some soy and rice peptides are used this way. Many modern formulas combine peptides from several of these groups so that they work through different pathways at the same time.

Peptide directory: the best-studied skincare peptides

The peptides in this section have the strongest research records of any cosmetic peptides, including at least some studies on human skin. They are listed from strongest evidence to weakest. The first name given for each is the INCI name, which is how it appears on an ingredient label.

Palmitoyl Pentapeptide-4 (Matrixyl, Pal-KTTKS)

Palmitoyl Pentapeptide-4 is the original Matrixyl and the most studied peptide in skincare. It is a signal peptide made of five amino acids, lysine, threonine, threonine, lysine and serine (KTTKS), taken from type I procollagen, the precursor to the most abundant collagen in human skin. In 1993, researchers showed in the laboratory that this pentapeptide stimulated the production of collagen and other components of the skin’s extracellular matrix. In 2005, a 12-week, vehicle-controlled, split-face study in women with photoaged facial skin found that a moisturizer containing Palmitoyl Pentapeptide-4 improved the appearance of wrinkles and fine lines compared with the same moisturizer without it, and it was well tolerated. Because a split-face study compares the peptide with an identical formula on the same person at the same time, it is one of the clearest ways to show that the ingredient itself is making the difference. Older products may list it as Palmitoyl Pentapeptide-3. Evidence rating: Moderate, and the strongest of any peptide in this guide.

Copper Tripeptide-1 (GHK-Cu, copper peptide)

Copper Tripeptide-1 is a carrier peptide made of three amino acids, glycine, histidine and lysine (GHK), bound to copper. GHK occurs naturally in the human body, and its levels are reported to decline with age. It has one of the largest bodies of laboratory research of any skincare peptide, with studies linking it to collagen production, wound healing, antioxidant activity and the regulation of many genes involved in skin repair. Small human studies have compared copper peptide creams with vitamin C and tretinoin creams. The laboratory evidence is extensive, but large, independent clinical trials on facial skin are still limited. Evidence rating: Moderate.

Acetyl Hexapeptide-8 (Argireline)

Acetyl Hexapeptide-8, sold as Argireline and sometimes listed as Acetyl Hexapeptide-3, is a neurotransmitter-inhibitor peptide. It is designed to interfere with part of the signal that tells facial muscles to contract, with the aim of softening the depth of expression lines such as crow’s feet and forehead lines. Several small human studies report modest improvements in the appearance of expression lines. The effect is real but much weaker than injectable botulinum toxin, and products that describe Argireline as “Botox in a bottle” overstate what it can do. Evidence rating: Moderate.

Palmitoyl Tripeptide-1 and Palmitoyl Tetrapeptide-7 (Matrixyl 3000)

Matrixyl 3000 combines two signal peptides. Palmitoyl Tripeptide-1 uses the same GHK sequence found in copper peptide, but without the copper, so it acts as a collagen signal rather than a mineral carrier. Palmitoyl Tetrapeptide-7, made of the sequence GQPR, is intended to calm the inflammatory signaling, including the messenger molecule interleukin-6, that contributes to collagen breakdown. Together they are designed to encourage collagen production while reducing the signals that break it down. Matrixyl 3000 is one of the most widely used peptide complexes in skincare, but most of its supporting data comes from the supplier. Older labels may list these ingredients as Palmitoyl Oligopeptide and Palmitoyl Tetrapeptide-3. Evidence rating: Moderate.

Peptide directory: newer peptides with emerging evidence

The peptides in this section are promising, but most of their evidence comes from laboratory studies, cell cultures or testing by the companies that supply them. Many are well designed and work through pathways that complement the better-studied peptides. They are rated Emerging or Unproven not because they are known to fail, but because independent studies on human skin have not yet been published.

Dipeptide Diaminobutyroyl Benzylamide Diacetate (Syn-Ake)

Syn-Ake is a neurotransmitter-inhibitor peptide inspired by a protein found in temple viper venom. It is designed to block the receptor on the muscle side of the nerve-to-muscle signal, which is a different point from the one Argireline targets. For that reason, the two are often used together to cover more of the pathway behind expression lines. Evidence rating: Emerging.

Palmitoyl Tripeptide-5 (Syn-Coll)

Palmitoyl Tripeptide-5 is a signal peptide that mimics a short sequence from thrombospondin-1, a natural protein that activates transforming growth factor beta (TGF-β). TGF-β is one of the skin’s main signals for producing collagen. The underlying biology, that thrombospondin activates TGF-β, was established in 1993, but published human data for the cosmetic peptide itself is limited. Evidence rating: Emerging.

Palmitoyl Tripeptide-38 (Matrixyl synthe’6)

Palmitoyl Tripeptide-38 is a signal peptide designed to support six major components of the skin’s structure at once, including several types of collagen and hyaluronic acid. The “6” in its trade name refers to these six components. Most of its evidence comes from supplier testing. Evidence rating: Emerging.

N-Prolyl Palmitoyl Tripeptide-56 Acetate (Matrixyl Morphomics)

N-Prolyl Palmitoyl Tripeptide-56 Acetate is the newest member of the Matrixyl family, developed by the ingredient supplier Sederma. It is a signal peptide intended to target the look of wrinkles and firmness. Because it is so new, its data comes almost entirely from the supplier. Evidence rating: Emerging.

Nonapeptide-1 (Melanostatine 5)

Nonapeptide-1 is a nine-amino-acid peptide designed to block the signal, carried by alpha-melanocyte-stimulating hormone, that tells skin cells to produce pigment. It is used to help even out the look of skin tone and dark spots rather than to firm skin. Evidence rating: Emerging.

Hexapeptide-11

Hexapeptide-11 is a six-amino-acid peptide that, in a 2015 laboratory study on human skin cells called fibroblasts, activated the cells’ own “proteostasis” systems, the housekeeping machinery that clears away and repairs damaged proteins. It is an interesting approach to supporting skin renewal, but it has not yet been tested in published studies on human skin. Evidence rating: Emerging.

Palmitoyl Hexapeptide-12

Palmitoyl Hexapeptide-12 is a signal peptide based on a repeating sequence found in elastin, the protein that lets skin snap back after it stretches. It is intended to support firmness and elasticity. Evidence rating: Emerging.

Acetyl Tetrapeptide-9 (Dermican)

Acetyl Tetrapeptide-9 is a signal peptide designed to boost lumican, a protein that helps collagen fibers form and organize properly. The aim is not only more collagen but better-organized collagen. Evidence rating: Emerging.

Decorin-mimicking tetrapeptide

Decorin is a natural skin protein that helps collagen fibers form with an even thickness and spacing. A decorin-mimicking tetrapeptide, described in research published in 2008, is designed to copy this role and help collagen fibers organize more evenly. Evidence rating: Emerging.

Tetrapeptide-21 (GEKG)

Tetrapeptide-21 is a short sequence of four amino acids, glycine, glutamic acid, lysine and glycine, found in collagen. It is intended to stimulate the production of collagen and other matrix components. Evidence rating: Emerging.

Arginine/Lysine Polypeptide

Arginine/Lysine Polypeptide is a chain made from the amino acids arginine and lysine. It is used as part of supplier peptide blends aimed at smoothing the look of expression lines. One supplier describes its blend as inspired by jellyfish peptides, but no published research on this ingredient is available. Evidence rating: Unproven.

Carnosine

Carnosine is a dipeptide, a peptide of just two amino acids, beta-alanine and histidine, that occurs naturally in the body. In skincare it is used as an antioxidant and to help protect proteins such as collagen from glycation, a type of damage caused when sugars bind to proteins and make them stiff. It is usually a supporting ingredient rather than a firming active. Evidence rating: Emerging.

What is the difference between Matrixyl, Matrixyl 3000, Matrixyl synthe’6 and Matrixyl Morphomics?

Matrixyl is a trade name used by the ingredient supplier Sederma, part of Croda, for a family of collagen-signaling peptides. The versions share a name, but they are different molecules, not stronger or weaker editions of the same ingredient. The original Matrixyl, released around 2000, is Palmitoyl Pentapeptide-4, the KTTKS sequence taken from procollagen, and it has the strongest human evidence of the family. Matrixyl 3000, released in the early 2000s, combines Palmitoyl Tripeptide-1 (the GHK sequence) and Palmitoyl Tetrapeptide-7 (the GQPR sequence) to support collagen while calming the inflammatory signals that break it down. Matrixyl synthe’6, released around 2010, is Palmitoyl Tripeptide-38, designed to support six components of the skin’s structure at once. Matrixyl Morphomics, the newest version, is N-Prolyl Palmitoyl Tripeptide-56 Acetate.

Because each version uses a different peptide, they send related signals in different ways. A label that simply says “contains Matrixyl” does not tell you which version is used or how much of it is in the formula, so it is always worth checking the full ingredient list. The newer versions are not necessarily better than the original. In terms of independent human research, the original Palmitoyl Pentapeptide-4 still has the strongest record.

Do peptides actually work? What they can and can’t do

Some peptides do work, but less dramatically than marketing suggests, and only when they reach the right layer of the skin in a meaningful amount. That is harder than it sounds. Skin is designed to keep things out, and a widely cited principle known as the “500 Dalton rule” holds that molecules larger than about 500 Daltons struggle to pass through the skin’s outer barrier. Many peptides are at or above that size. Formulators often attach a fatty acid chain, the “palmitoyl” in many peptide names, to help them move through the skin’s lipid layers. The rest of the formula, including its base, pH and delivery system, also affects how much of a peptide actually reaches living skin cells.

Concentration matters just as much. A peptide listed near the end of an ingredient list may be present at a level far below what was used in the studies. It also helps to know that many peptides are sold to brands as ready-made solutions, in which the peptide is dissolved in water and other carriers, so the percentage of a “peptide complex” in a product is not the same as the percentage of pure peptide. Many claims come from cells in a laboratory dish, and human skin, over weeks of real use, is a much harder test. A 2019 systematic review of matrix-stimulating peptides used in anti-aging cosmetics found that many widely used peptides had little independent clinical testing.

There is good news, too. Well-made formulas containing peptides have performed well in studies. A 2010 trial found that a cosmetic regimen combining niacinamide, peptides and retinyl propionate produced results comparable to 0.02% prescription tretinoin over the study period, with better tolerability. Peptides are also gentle, rarely irritating and easy to combine with other ingredients, which makes them a useful supporting ingredient in almost any routine.

How to use peptides in your skincare routine

Peptides are among the gentlest active ingredients in skincare, and they fit easily into most routines. The most important step is not a peptide at all. Daily sunscreen does more to protect aging skin than any peptide can, because ultraviolet light is one of the main causes of collagen breakdown. Once sun protection is in place, choose peptides in leave-on products such as serums, concentrates and moisturizers, which stay on the skin long enough to work. Peptides in cleansers are rinsed away before they can do much.

Peptides pair well with niacinamide, hyaluronic acid, ceramides and retinoids. Apply them to clean skin, after any watery toners or essences and before heavier creams or oils. Be patient: most studies measure results after eight to twelve weeks of consistent daily use. If a product makes skin feel tighter or smoother the moment you apply it, that instant effect usually comes from other ingredients, such as film-formers and emollients, while the peptides work more slowly over weeks. When shopping, read the full ingredient list rather than the front of the box, check where the peptide appears in the list, and look for brands that are open about which peptides they use and how much. Be wary of promises such as “Botox in a bottle” or “rebuilds collagen overnight,” which go well beyond what the research supports. If you are pregnant, have a skin condition or are under a dermatologist’s care, check with your doctor before adding new active ingredients.

The peptides in FIRÈNE™ and LAMELLARE™

We use peptides in our own formulas because we believe the best of them earn their place, and we want to be as open about our products as we are about the research. FIRÈNE™ and LAMELLARE™ use different peptides for different jobs, and they are designed to complement each other rather than repeat each other.

FIRÈNE™, our Multi-Peptide Firming Concentré, is built around signaling. It contains eight peptides from two professional peptide complexes, DermaTide Smooth Plus and Matrixyl Morphomics, which together make up 6.46% of the formula, targeting firmness, expression lines and tone. At its core are two generations of Matrixyl: Matrixyl 3000 (Palmitoyl Tripeptide-1 and Palmitoyl Tetrapeptide-7) to support collagen while calming the signals that break it down, and Matrixyl Morphomics (N-Prolyl Palmitoyl Tripeptide-56 Acetate), the newest member of the family. Syn-Coll (Palmitoyl Tripeptide-5) adds a second route to collagen support by mimicking a natural activator of collagen production. For expression lines, FIRÈNE™ combines Argireline (Acetyl Hexapeptide-8) and Syn-Ake (Dipeptide Diaminobutyroyl Benzylamide Diacetate), which act at two different points in the nerve-to-muscle signal. Nonapeptide-1 helps even out the look of skin tone, and Arginine/Lysine Polypeptide is part of the same expression-line complex. FIRÈNE™ also contains carnosine, an antioxidant dipeptide that helps protect proteins like collagen from damage caused by sugars.

LAMELLARE™, our GHK-Cu Structural Crème, is built around repair. It contains three peptides chosen to support the skin’s own renewal. Copper peptide (Copper Tripeptide-1, GHK-Cu) delivers copper to the skin’s repair enzymes and has the deepest research record of any peptide we use. Matrixyl synthe’6 (Palmitoyl Tripeptide-38) supports several components of the skin’s structure at once. Hexapeptide-11 activated the cells’ own protein-repair systems in laboratory research. These peptides are set in a base of multi-lamellar ceramides, cholesterol and phytosphingosine, the same kinds of lipids that hold a healthy skin barrier together.

How FIRÈNE™ and LAMELLARE™ work together

The two formulas follow the same thinking as The Layland Method™, our signature skin protocol. FIRÈNE™ sends signals to the skin: build collagen, soften expression lines and even out tone. LAMELLARE™ supplies what the skin needs to answer those signals: copper for its repair enzymes, support for its structure and the lipids a stressed barrier needs to rebuild. A signal is only useful if the skin has the resources and the time to respond. That is why LAMELLARE™ is designed for rest nights, when skin is recovering from active treatments, and why its peptides lean toward repair rather than challenge.

Why these peptides earned a place in our formulas

We chose every peptide by asking three questions. First, is there published research behind it? Matrixyl 3000, Argireline and copper peptide have the longest records, including studies on human skin, so they anchor our formulas: copper peptide in LAMELLARE™, and Argireline and Matrixyl 3000 in FIRÈNE™. Second, does it do a different job from everything else in the formula? Each of our peptides works through a different pathway, so none of them is filler or a repeat of another. Third, is it present at a level that matters? In FIRÈNE™, the two peptide complexes make up 6.46% of the formula, a meaningful level rather than a token amount. Some of the peptides we use are newer, and their evidence is still emerging. We include them because their pathways complement the better-studied peptides, and we rate them honestly in this guide so you know exactly what to expect.

Frequently asked questions about skincare peptides

What do peptides do for your skin?

Peptides are short chains of amino acids that act as messengers in the skin. Depending on the type, they can signal skin cells to produce more collagen, deliver minerals such as copper that support repair, or soften the muscle signaling behind expression lines. Their effects are gradual and work best as part of a routine that includes daily sunscreen.

Do peptide serums actually work?

Some do. The best-studied peptides, including Palmitoyl Pentapeptide-4 (Matrixyl), copper peptide (GHK-Cu), Argireline and Matrixyl 3000, have at least some published studies on human skin showing modest improvements in wrinkles, firmness or expression lines. Many other peptides have mostly laboratory or supplier data, so their real-world results are less certain. The formula and the concentration matter as much as the peptide itself.

Which peptide has the most scientific evidence?

Palmitoyl Pentapeptide-4, the original Matrixyl, has the strongest research record of any cosmetic peptide, including laboratory work from 1993 and a 2005 controlled split-face study in women with photoaged skin. Copper peptide (GHK-Cu) has the largest body of laboratory research.

Are peptides better than retinol?

No. Retinoids, including retinol and prescription tretinoin, have much stronger evidence for improving wrinkles and skin texture than any peptide. Peptides are gentler and less likely to irritate, which makes them a good partner to retinoids rather than a replacement.

Can I use peptides with retinol, vitamin C or acids?

Yes. Peptides are compatible with most skincare ingredients, including retinoids, niacinamide, hyaluronic acid and ceramides. Many people use peptides on the nights they rest from retinoids or exfoliating acids to support recovery.

How long do peptides take to work?

Most studies measure results after eight to twelve weeks of consistent daily use. Any instant tightening or smoothing you feel when you apply a product usually comes from other ingredients in the formula.

Is Argireline the same as Botox?

No. Argireline (Acetyl Hexapeptide-8) is designed to soften the look of expression lines by interfering with part of the nerve-to-muscle signal, but its effects are modest and much weaker than injectable botulinum toxin.

What is the difference between copper peptide and Matrixyl 3000?

Both use the same three-amino-acid sequence, GHK. In copper peptide (GHK-Cu), it is bound to copper and acts as a carrier that delivers copper to repair enzymes. In Matrixyl 3000, it is attached to a fatty acid chain as Palmitoyl Tripeptide-1 and acts as a collagen signal, paired with a second peptide that calms inflammation.

About this version and what comes next

This is Version 1 of The Steinder Weisen Peptide Guide, published in October 2026. It reflects the published research, supplier information and formulation experience available to us at the time of writing. Science does not stand still, and neither will this guide. We will continue to review new studies, gather data from our suppliers and our own formulation work, and release updated versions as the evidence develops. Future versions may add peptides that are not covered here, change evidence ratings up or down as new research appears, and include results from testing on our own finished products. Each new version will be dated and will note what has changed, so you can always see how our understanding has evolved.

We are also continuing to develop new formulas. Palmitoyl Pentapeptide-4, the peptide with the longest scientific record, is next on our bench, and we will share more as that work progresses. If there is a peptide you would like us to research for the next version of this guide, we would love to hear from you.

Sources

• Katayama et al., A pentapeptide from type I procollagen promotes extracellular matrix production (J Biol Chem, 1993)

• Robinson et al., Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin (Int J Cosmet Sci, 2005)

• Peptides stimulating synthesis of extracellular matrix used in anti-ageing cosmetics: are they clinically tested? A systematic review (2019)

• Fu et al., Cosmetic niacinamide/peptide/retinyl propionate regimen vs. 0.02% tretinoin (Br J Dermatol, 2010)

• Abdulghani et al., Effects of topical creams containing vitamin C, a copper-binding peptide cream and melatonin compared with tretinoin

• Pickart et al., GHK peptide as a natural modulator of multiple cellular pathways in skin regeneration (2015)

• Sklirou et al., Hexapeptide-11 is a novel modulator of the proteostasis network in human diploid fibroblasts (Redox Biol, 2015)

• Lintner et al., A serum containing vitamins C & E and a matrix-repair tripeptide reduces facial signs of aging (2020)

• Schultz-Cherry & Murphy-Ullrich, Thrombospondin causes activation of latent TGF-β (J Cell Biol, 1993)

• Bos & Meinardi, The 500 Dalton rule for the skin penetration of chemical compounds and drugs (Exp Dermatol, 2000)

• Puig et al., A new decorin-like tetrapeptide for optimal organization of collagen fibres (2008)

• Signal, carrier and neurotransmitter-inhibitor peptides in cosmetics: a review (Romanian J Pharm Practice, 2021)

• Palmitoyl tripeptide-38 ingredient profile (INCIDecoder)

• Palmitoyl tetrapeptide-7 ingredient profile (INCIDecoder)

• Palmitoyl hexapeptide-12 ingredient profile (INCIDecoder)

• Tetrapeptide-21 (GEKG) overview

• Acetyl tetrapeptide-9 technical information (Cayman Chemical)

• DermaTide Smooth Plus product information (Dermegen)

The Steinder Weisen Peptide Guide, Version 1, October 2026. This guide is for education only and is not medical advice.