Peptides for the skin: what they are and which one to choose

Peptides, also known as polypeptides, are short chains of amino acids: the same building blocks that the skin uses to build its structural proteins. They occur naturally in the skin and are now among the most widely used active ingredients in anti-aging cosmetics.

Collagen is made up of three polypeptide chains: this relationship explains why certain peptides, when applied to the skin, may support the processes that lead to its production.

The body naturally produces collagen, but over time this production decreases, and the skin appears more marked, less even, and dull. Is it worth investing in peptide-rich products? What types are available, and how do you choose the most suitable formulation?

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What are peptides?

Peptides are chains of amino acids, or the "building blocks" of proteins. They serve as building blocks not only for collagen but also for elastin fibers, which give tissues firmness and elasticity. If you would like to learn more about the role of individual amino acids, we discuss it in our guide to amino acids in cosmetics.

In addition to being structural components, peptides often act as biological messengers: they carry instructions from one cell to another. This is their most interesting characteristic in cosmetics.

Because they are much smaller molecules than whole proteins, peptides also have a practical advantage: they cross the stratum corneum more effectively, whereas a complete protein such as collagen remains on the surface.

Peptides, polypeptides, and proteins: what is the difference?

The three terms indicate the same thing — chains of amino acids linked together — and differ only in length. The most widely used convention in biochemistry is as follows:

• Oligopeptides: from 2 to approximately 10 amino acids. A bond between two amino acids produces a dipeptide, between three a tripeptide, and so on.
• Polypeptides: approximately 10 to 50 amino acids.
• Proteins: more than 50 amino acids, with a folded three-dimensional structure that determines their function.

The boundary is not clear-cut and varies slightly from one text to another, but the substance is that a polypeptide is simply a long peptide. In cosmetics, the lower range is used almost exclusively, from two to six amino acids: these are molecules small enough to cross the stratum corneum, which is why labels feature names such as tripeptide, tetrapeptide, or hexapeptide followed by a number.

One useful clarification: when a peptide is applied to the skin, its action is local. The peptides discussed in oral supplements—those from collagen or creatine—follow a completely different pathway and should not be confused with cosmetic peptides, even when their names are similar.

How peptides work on the skin

If peptides are already present in the skin, why add more? The answer is skin aging. After the age of 30, collagen production gradually declines, and the signals that regulate renewal become less efficient.

Peptides do not work like a traditional active ingredient: they are signals. They communicate with dermal fibroblasts, prompting them to activate and produce new collagen, elastin, and hyaluronic acid. In a sense, they recreate the message that youthful skin sends itself more frequently.

This gives peptides their main characteristic: they work cumulatively. The results are not immediate and require weeks of consistent application, but they develop progressively.

Types of peptides

Not all peptides are the same: there are four families, and they do different things. Understanding this is the best way to choose one product over another.

Peptides that act on neuromuscular transmission

They reduce the intensity with which the facial muscles contract, so that the lines caused by repeated movement appear less pronounced. The effect is gradual, superficial, and reversible: it lasts as long as the product is used consistently. A study published in the International Journal of Cosmetic Science in 2002 (Blanes-Mira et al.) reported an approximately 30% reduction in wrinkle depth after 30 days of application, although the sample consisted of very few volunteers. The peptides in this group include:

• Acetyl Hexapeptide-8: also known as Argireline®, it interferes with the SNAP-25 protein, thereby reducing the amount of acetylcholine released at the neuromuscular junction.
• Acetyl Hexapeptide-1: also known as Munapsys™, the latest biomimetic peptide with a dual mode of action. It is the most suitable choice for dynamic forehead and glabellar wrinkles.
• Palmitoyl Hexapeptide-19 and Tripeptide-3.

Signal peptides

They are the most widespread: they signal fibroblasts to produce collagen, elastin, and other structural proteins. Among the best known:

• Palmitoyl Pentapeptide-4, known as Matrixyl®: it does not act on muscle contraction, but on the production of new collagen and hyaluronic acid. For this reason, it is often paired with Argireline®, which works on a completely different front.
• Palmitoyl Tripeptide-1, Palmitoyl Tripeptide-5, and Palmitoyl Tripeptide-38, all aimed at collagen synthesis.
• Tripeptide-1 (GHK), among the most extensively studied in the literature.
• Oligopeptide-10, used for its effect on the balance of the skin's surface.

Carrier peptides

They are named for their role: delivering trace elements such as copper and magnesium where they are needed. Copper has been particularly studied for its role in collagen-related processes, and copper complexes help even out the complexion by counteracting photoaging.

The best known is GHK-Cu, or copper peptide: a signal peptide that becomes a carrier when it forms complexes with copper.

Enzyme-inhibiting peptides

They act by slowing the degradation of existing collagen rather than stimulating new collagen production. It is a complementary approach: build on one side, protect on the other. These include:

• Dipeptide-2 and Acetyl Tetrapeptide-5, known as Eyeseryl®: promotes fluid drainage and reduces the puffy appearance of the under-eye area. It is the peptide of choice for bags and dark circles.
• Acetyl Tetrapeptide-40: inhibits the release of pro-inflammatory interleukins and, consequently, the activation of metalloproteinases that break down collagen and elastin. It is the peptide of choice for persistent redness and couperose.
• Oligopeptide-20 and peptides derived from rice proteins and soy.

Silk peptides: a category of their own

Alongside the four active families, there is a group that follows a different logic: peptides of hydrolyzed protein origin. Silk peptides are the best-known example, and on labels they appear as Hydrolyzed Silk, Serica or Hydrolyzed Sericin.

The substantial difference compared with biomimetic peptides is that silk peptides do not transmit a signal to fibroblasts. They work on the surface, where they form a thin film that retains water and reflects light more evenly. The effect is immediate and noticeable — smooth skin to the touch and a more even complexion — but it does not alter the structure of the dermis as a signal peptide does. They are two tools for two different goals, not alternatives to one another.

Where they come from, what studies say about sericin, why they are not included in vegan formulas and how to identify them on the label: the complete overview is in the article dedicated to silk peptides.

The main benefits of products containing peptides

The collagen molecule is too large to cross the stratum corneum: when applied to the skin, it remains on the surface and hydrates, but it does not rebuild anything. Peptides, being much smaller, can instead reach the layers where the signal is needed. This is why they have replaced collagen in the most advanced anti-ageing formulas.

1. They support the skin barrier: the skin barrier is the first line of defence against pollution, UV rays and external aggressors. Peptides help keep it intact.
2. They reduce the appearance of wrinkles: this is their best-known use, achieved by supporting collagen production, which makes the skin firmer and plumper.
3. They improve elasticity: peptides are also the building blocks of elastin fibres, which allow the skin to return to its original position.
4. They contribute to a more even appearance of blemished skin: some peptides support the balance of the skin's surface, improving the appearance of imperfections.

The benefits of peptides emerge through consistent, prolonged use: this is what distinguishes them and, at the same time, the condition for them to work.

LeLang peptide formulas

Formula Eyes Duo Peptide is formulated with two targeted-action peptides: Acetyl Hexapeptide-8 and Acetyl Tetrapeptide-5.

The first reduces the intensity of the signal that causes the contraction of the facial muscles, while the second promotes fluid drainage. Together, they improve the appearance of bags and dark circles and soften under-eye wrinkles. Hyaluronic acid and caffeine complete the formula: the former for hydration and the latter for microcirculation.

The eye contour is a particularly delicate area, where the skin is thin and signs are more visible; it should be treated differently from the rest of the face. We have dedicated a complete guide to the eye area, with treatments suitable for every age.

Vitis Eyes Contour combines the same two peptides with red vine extract and hyaluronic acid in a richer texture designed for mature skin.

For the face, Perlage cream focuses on Amplified Argireline, with a noticeable tightening effect from the first applications, enriched with vitamin E released gradually.

For more pronounced expression lines on the forehead and glabella, we chose a more recent-generation peptide, Munapsys™, formulated in the Multi Peptide Lift serum.

For skin prone to redness, there is Couper Relief, formulated with Acetyl Tetrapeptide-40: the dedicated page explains how it works on redness and couperose.

The peptide ingredient page contains the complete list of LeLang formulas that contain them.

Frequently asked questions about peptides

What is the difference between peptides and polypeptides?

Only the length of the chain. We speak of oligopeptides of up to around ten amino acids, polypeptides of approximately ten to fifty, and proteins of more than fifty. A polypeptide is therefore a long peptide, not a molecule of a different nature. In cosmetics, almost exclusively short chains of two to six amino acids are used because they are the only ones small enough to cross the stratum corneum.

Where are peptides found?

They are found wherever there are proteins. The body produces them continuously—insulin and oxytocin are peptides—and they are also formed during the digestion of any protein-rich food, from meat to legumes. In the skin, they are part of the structure of collagen and elastin. In cosmetics, however, biomimetic peptides synthesized in the laboratory are used, selected individually according to the signal they need to transmit: this is different from the peptides obtained through the diet.

What are silk peptides?

They are fragments obtained by hydrolyzing the proteins in silkworm cocoons, fibroin and sericin, and appear on labels as Hydrolyzed Silk or Serica. Unlike biomimetic peptides, they do not transmit signals to fibroblasts: they form a surface film that retains water, making the skin feel smooth and the complexion look more even. The effect is immediate and sensory, not structural. We discuss them in detail in the article on silk peptides.

How long does it take for peptides to work?

They work cumulatively: the first noticeable differences appear after four to eight weeks of consistent use, while improved firmness takes longer. Anyone who changes products after two weeks does not give any peptide a chance to work.

Are peptides or retinol better?

They do different things. Retinol acts on cell renewal and is more potent but also more irritating; peptides work on signaling and are much better tolerated. In well-designed routines, they coexist, with the retinoid at night and peptides in the morning.

Can they be used with vitamin C and hyaluronic acid?

Yes, without any problems. Peptides are among the most compatible actives available: they do not require a specific pH and have no known incompatibilities with the most common ingredients.

What age is it best to start?

Signal peptides make sense from the point when collagen production begins to decline, roughly from the age of thirty. Those targeting expression lines follow the appearance of the first dynamic lines, which can occur even earlier.

Are peptides suitable for sensitive skin?

Yes, and that is one of their greatest advantages: they have a very good tolerability profile and do not cause the irritation typically associated with retinoids and acids. They are often the anti-aging choice for people who cannot tolerate more aggressive actives.

How do I recognize them on the label?

Look for names beginning with Acetyl, Palmitoyl, or containing -peptide followed by a number. Trade names such as Argireline or Matrixyl do not appear in INCI; instead, you will find the molecule's designation.