This article covers the ground of two Polish articles on peptides in skincare: peptides and skin radiance and peptides in cosmetic formulations.
Cosmetic peptides are short chains of amino acids, usually 3 to 30 residues and at most about 50, that are added to skincare products to talk to skin cells rather than to sit on the surface. They are divided into four groups by mechanism: signal peptides, neurotransmitter-inhibiting peptides, carrier peptides and enzyme-inhibiting peptides. Each does something different, and knowing which group an ingredient belongs to says more than the marketing name on the box.
Why the skin loses firmness in the first place
Skin is the largest organ of the body. Over the years, under ultraviolet radiation, oxidative stress and hormonal change, it loses firmness and its capacity to regenerate, because it produces less of the key structural proteins, collagen and elastin. Cosmetic peptides are aimed at that process: they are meant to support the skin’s own repair mechanisms rather than to add material from outside.
Peptides are not proteins
A peptide is a short chain of amino acids joined by peptide bonds, typically 3 to 30 residues. Proteins are far longer, usually 100 amino acids or more. That difference in size is what matters in cosmetics, because a smaller molecule has a better chance of penetrating the epidermis. Peptides are bioactive, taking part in processes such as homeostasis, immunity, regeneration and defence against pathogens, and they can be natural, obtained from proteins, plants or marine animals, or synthetic and biomimetic. The full comparison is in the article on peptides versus proteins.
The four types of cosmetic peptide
1. Signal peptides, also called matrikines
These act as messengers to the skin’s cells, above all to fibroblasts, the cells that produce the structural components of the extracellular matrix. Stimulated fibroblasts increase the synthesis of collagen, particularly types I and III, of elastin, fibronectin, glycosaminoglycans and proteoglycans. The intended result is skin that regains elasticity and firmness, with shallower wrinkles. Signal peptides can also act like growth factors, activating protein kinase C, which matters for cell growth and migration.
The best known example is palmitoyl pentapeptide-4, sold under the name Matrixyl.
2. Neurotransmitter-inhibiting peptides
This group is popular because its mechanism resembles that of botulinum toxin, while being applied non-invasively. These peptides reduce contraction of the muscles of facial expression by interfering with the SNARE complex, which is needed to release acetylcholine at the neuromuscular junction. Blocking that process relaxes the muscle and makes expression lines such as crow’s feet and forehead lines less visible.
Acetyl hexapeptide-3, known as Argireline, is a synthetic peptide imitating the N-terminal fragment of the SNAP-25 protein; its effect becomes visible after about a month. Tripeptide-3, known as SYN-AKE, is a biomimetic acetylcholine receptor antagonist modelled on waglerin-1, a protein from snake venom, and it can give an almost immediate smoothing effect, which is why it is added to speed up visible results.
3. Carrier peptides
These work as a taxi for trace elements, delivering copper (II) or manganese to skin cells. Copper is needed by enzymes such as lysyl oxidase and superoxide dismutase, which take part in wound healing and collagen synthesis. The effect sought is support for regeneration and tissue repair, along with antioxidant action.
The example is copper tripeptide-1, GHK-Cu, a tripeptide that occurs naturally in human plasma, has a strong affinity for copper ions and is released during collagen production.
4. Enzyme-inhibiting peptides
With age and under external factors such as ultraviolet radiation, the skin increases the activity of enzymes that break down collagen and elastin. These peptides inhibit those enzymes, above all the matrix metalloproteinases responsible for degrading matrix proteins. Some also stimulate the gene for hyaluronan synthase 2 in keratinocytes.
Examples include soy peptides, which act as proteinase inhibitors and protect against ultraviolet damage, rice peptides, which inhibit matrix metalloproteinases and stimulate hyaluronan synthase 2, and silk peptides, which show antioxidant and anti-inflammatory activity.
The obstacle: peptides penetrate skin poorly
For all their mechanisms, peptides face one large problem. The stratum corneum, the outer barrier of the skin, is lipophilic and blocks the passage of large water-loving molecules, and most peptides are exactly that. To cross it well, a molecule should have a small mass, under about 500 daltons.
Three approaches are used to get peptides deeper:
- Chemical modification, for example attaching a palmitoyl group to raise lipophilicity, as in palmitoyl pentapeptide-4.
- Carrier systems such as liposomes, nanoemulsions and niosomes, microscopic structures that protect the peptide and help it through the stratum corneum.
- Physical methods such as microneedling, radiofrequency and iontophoresis, which create temporary microchannels in the skin.
What this shop actually sells
The molecules described above are cosmetic ingredients, added to creams and serums. This shop does not sell cosmetics. The skin-related peptides in the range, collected in the skin and longevity peptides category, are supplied as research material, in lyophilised form, and they are not a finished skincare product. That distinction matters: the evidence described in this article concerns topical cosmetic formulations, not injections, and the terms of purchase are set out on the legal warning page.
Cosmetic ingredient law is less restrictive than pharmaceutical law, and knowledge of the long-term safety of these molecules is still developing. That is a reason to read the mechanism rather than the marketing claim.
Frequently asked questions
How do peptides work in a cream?
They act as signals to skin cells: they stimulate fibroblasts to produce collagen and elastin, relax the muscles of facial expression, carry trace elements or inhibit enzymes that degrade collagen. Which of these happens depends on the group the peptide belongs to.
Are peptides a replacement for botulinum toxin?
No. Neurotransmitter-inhibiting peptides work on a similar principle, by limiting the release of acetylcholine, but they are applied to the surface of the skin and their effect is weaker and slower than an injection.
Why do peptides penetrate the skin poorly?
Because the stratum corneum is lipophilic and blocks large water-loving molecules. A molecule under about 500 daltons crosses it best, which is why formulators use chemical modification and carrier systems.
What is GHK-Cu?
A copper tripeptide that occurs naturally in human plasma. In cosmetics it works as a carrier peptide, delivering copper ions used in wound healing and collagen synthesis.
Do the peptides in this shop work like cosmetics?
They are not cosmetics. They are supplied as research material in lyophilised form, and the evidence described here concerns topical cosmetic formulations.