Peptides in cosmetics – what are they, and what is their function?
Peptides have become a permanent element of cosmetic formulations, and claims that are difficult to substantiate have arisen around them.
Peptides have become a permanent element of cosmetic formulations, and claims that are difficult to substantiate have arisen around them. This article organizes three things that usually go together in such lists: how peptides are classified by function, what the data actually show and – most often omitted – what is the legal status of a given molecule, because the same substance can exist in three different regulatory roles.
However, we start not with promises, but with the barrier that limits this entire category.
Status information. The peptides discussed in this article appear in various regulatory roles: as ingredients of finished cosmetics subject to Regulation (EC) No. 1223/2009, as raw materials for formulations and – in the case of GHK-Cu – as research reagents in the form of injection. These are not interchangeable categories. The material is informative.
A barrier that needs to be mentioned first
The effectiveness of a peptide in a cosmetic depends not only on what it does to the cell, but above all on whether it reaches the target at all. The stratum corneum is a barrier designed to retain molecules from the outside, and peptides have two characteristics that make it difficult to overcome: they are hydrophilic and relatively large for candidates for transdermal penetration.
It follows that claims about “stimulating collagen synthesis in the dermis” require the separation of two questions, which appear as one in marketing materials:
- Does the peptide have an effect on the cell? This question is answered by research on fibroblast cultures – and for many peptides the answer is affirmative.
- Does the peptide reach this cell from cream? This is a separate, much more difficult question, and the answer is sometimes much less clear.
This problem is discussed directly in studies devoted to the topical use of peptides – for example, in the analysis of GHK as an anti-wrinkle peptide, where, in addition to the advantages, problems and limitations of this path are also listed applications (Mortazavi et al., 2024, PMID 39963574). Similarly, in the review on acetylhexapeptide-8, the issue of penetration through the skin was treated on an equal footing with the effectiveness of (Zdrada-Nowak et al., 2025, PMID 40565185). Much of the development in this field today concerns not new peptides, but carrier technologies, which are intended to solve this problem.
Three legal frameworks for the same molecule
This distinction determines what can be said about a given ingredient – and can be a source of real misunderstandings.
| Character | Legal framework | What can be said communicate |
|---|---|---|
| Ingredient of the finished cosmetic
(cream, serum) |
Regulation (EC) No. 1223/2009 | cosmetic effect – skin appearance, hydration, visibility of wrinkles. Never action medicinal. |
| Raw material for formulation
(peptide powder, base) |
material for research use | chemical characteristics and mechanism; no claims for human effects |
| Injection reagent
(e.g. GHK-Cu in vial) |
Research Use Only | research context only; not for human use |
Consequence practical: the same name on the label does not mean the same product category. A peptide sold as a raw material for self-formulation is not a cosmetic – only a finished product subject to a safety assessment and documentation required by the regulation becomes a cosmetic. We discuss a broader map of the regulatory statuses in the offer at compounds tested in androgenic alopecia.
Functional groups of cosmetic peptides
The division into four groups corresponds to different mechanisms, not different “potencies of action”. Current reviews on peptides in the context of skin aging organize this taxonomy (Pintea et al., 2025, PMID 39858482), (Pai et al., 2017, PMID 27451932).
Signaling peptides
Imitate fragments produced during the breakdown of collagen. The logic of the mechanism is elegant: the presence of such fragments is a signal for the fibroblast of matrix damage, and therefore a stimulus for the synthesis of new collagen. This group includes peptides from the family Matrixyl — palmitoylated pentapeptide-4 and complexes with palmitoylated tripeptide-1 and tetrapeptide-7.
Data for this group come largely from cell cultures and research on ready-made multi-component formulations. Among other things, the influence of various application forms on healing in the model in vivo (Kachooeian et al., 2022, PMID 35874243) and the effect of multi-component preparations containing peptides (Yang et al., 2024, PMID 38932444). It is worth noting this directly: when testing a multi-component formulation, the result cannot be assigned to a single peptide.
Peptides affecting neuromuscular transmission
The most recognizable group, which includes argireline (acetylhexapeptide-8) and SNAP-8 (acetyl octapeptide-3). The mechanism is based on interference with the SNARE protein complex, involved in the release of a neurotransmitter at the neuromuscular junction – hence the colloquial term for this group by analogy to botulinum toxin.
The anti-wrinkle activity of argireline was described in a 2002 paper (Blanes-Mira et al., 2002, PMID 18498523), and the current review combines efficacy data along with skin penetration data (PMID 40565185). This juxtaposition is important: the analogy to botulinum toxin concerns only the general direction of the mechanism, not the strength of the effect or the route of administration.
Carrier peptides
Transport metal ions to the place where they are needed as enzymatic cofactors. The main representative is GHK-Cu, discussed separately below.
Enzyme-inhibiting peptides
Reduce the activity of enzymes that degrade extracellular matrix proteins, primarily metalloproteinases. The mechanism is conservative – it concerns limiting degradation, not stimulating synthesis.
GHK-Cu – the same tripeptide in two roles
GHK-Cu is a complex of glycyl-histidyl-lysine tripeptide with a copper ion. It is the best described peptide in this category and at the same time the best example of why the separation of regulatory frameworks is important.
Mechanism
The described action includes signaling of extracellular matrix remodeling, influence on gene expression, anti-inflammatory and antioxidant activity, and participation in repair processes. An extensive discussion of these issues, along with gene expression data, is provided in the review (Pickart and Margolina, 2018, PMID 29986520); the potential of this tripeptide in the context of aging was also discussed separately (Dou et al., 2020, PMID 35083444).
Two forms, two regimes
- In cosmetics — GHK-Cu is an ingredient of a finished product subject to the cosmetics regulation. Communication is limited to cosmetic effects: the appearance of the skin, its hydration, the visibility of wrinkles. Penetration through the stratum corneum remains a limitation (PMID 39963574).
- As an injection reagent — GHK-Cu also comes in the form of a lyophilized vial, intended for research use only. It is not a cosmetic and is not intended for use on humans. Observations from research on this form do not transfer to a cosmetic product – and vice versa.
The mixing of these two contexts is the most common error in GHK-Cu descriptions. Data from models in which the peptide was administered systemically or directly to culture are sometimes cited to justify the cream’s effect – even though they differ in the route of administration, concentration and availability of the molecule.
How to read research on cosmetic peptides
A few distinctions that organize the reading of this literature:
- Cell culture vs. skin. Peptide added directly to fibroblast cultures bypasses the epidermal barrier entirely. The result of such a test speaks about the properties of the molecule, not about the effectiveness of the cosmetic.
- Formulation and ingredient. The examination of a ready-made cream containing several active substances does not determine the contribution of any of them separately.
- End point. Improvement of an instrumental parameter, evaluation on a subjective scale and histological change are three different things.
- Sample size and follow-up time. In cosmetic studies, samples can be small and follow-up short, limiting the strength of conclusions.
The broader context of anti-aging strategies, in which peptides are one of many approaches, is presented in reviews (Griffiths et al., 2023, PMID 37903073), (Chan et al., 2024, PMID 39233460). It is worth remembering that part of the observed improvement in the appearance of the skin when using any topical preparation is due to the moisturization and properties of the base (Draelos, 2018, PMID 29319217).
Regulatory status
Ready-made cosmetics are subject in the European Union to Regulation (EC) No. 1223/2009, which imposes the obligation to prepare a safety report, maintain product documentation and report it to the notification portal. In doing so, claims must meet the requirements of Regulation (EU) No 655/2013 on the criteria for substantiating claims.
These provisions result in a fundamental limitation for the entire category: the cosmetic affects the appearance and condition of the skin, it does not cure. Claims suggesting a therapeutic effect are unacceptable in cosmetic communications, regardless of what has been demonstrated for the molecule itself under other conditions.
Peptide raw materials intended for self-formulation and injectable forms are not cosmetics and are subject to separate rules – in the case of the latter, the regime of material intended only for research applies.
Frequently asked questions
Do peptides in the cream reach the dermis?
This is an open question, and penetration through the epidermal barrier remains one of the main limitations of this category. Peptides are hydrophilic and relatively large, which makes it difficult for them to penetrate the stratum corneum. Much of the development work today concerns carrier technologies to solve this problem.
Has the effectiveness of Matrixyl been “clinically proven”?
Such a formulation is too strong. The available data comes largely from cell cultures and studies on ready-made multi-component formulations, in which the contribution of a single peptide cannot be isolated. It is more conservative and consistent with the data to say that the studies suggest an impact on processes related to the synthesis of matrix components.
Is GHK-Cu in cream the same as GHK-Cu in a vial?
Same molecule, two different product categories. In a cosmetic it is an ingredient subject to the cosmetics regulation, in a vial it is a reagent intended only for research purposes, not intended for use on humans. Observations from one context do not carry over to another.
Does argireline act like botulinum toxin?
The analogy is to the general direction of the mechanism – SNARE complex interference – not to potency, route of administration, or product category. Botulinum toxin is a medicinal product administered by injection by medical personnel.
Are cosmetic peptides safe?
Finished cosmetics placed on the market in the European Union are subject to mandatory safety assessment under Regulation 1223/2009. Independent preparation of preparations from raw materials does not cover such an assessment.
Summary
Cosmetic peptides are divided into four functional groups – signaling, affecting neuromuscular transmission, carrier and enzyme inhibitory – and this division corresponds to different mechanisms, not different potency. The limitation common to the entire category is penetration through the stratum corneum: peptides are hydrophilic and relatively large, so the result obtained in cell culture does not automatically translate into the effectiveness of the preparation applied to the skin. For this reason, statements like “clinically proven” are too strong for most of these ingredients – the data suggests effects on specific processes, which is a weaker and fairer claim. The legal status requires a separate distinction: the same molecule may appear as an ingredient of a finished cosmetic covered by Regulation (EC) No. 1223/2009, as a raw material for formulation and – in the case of GHK-Cu – as an injection reagent intended solely for research. These are three separate categories, and observations do not transfer between them.
Product documentation
Ingredient cards along with batch analytical documentation are available in the category peptide cosmetics. Peptide injection forms are materials intended for research use only.
Bibliography
- Pintea A, Manea A, Pintea C, et al. Peptides: Emerging Candidates for the Prevention and Treatment of Skin Senescence: A Review. Biomolecules. 2025;15(1):88. PMID: 39858482
- Pai VV, Bhandari P, Shukla P. Topical peptides as cosmeceuticals. Indian J Dermatol Venereol Leprol. 2017;83(1):9-18. PMID: 27451932
- Mortazavi SM, Mohammadi Vadoud SA, Moghimi HR. Topically applied GHK as an anti-wrinkle peptide: Advantages, problems and prospective. Bioimpacts. 2024;15:30071. PMID: 39963574
- Zdrada-Nowak J, Surgiel-Gemza A, Szatkowska M. Acetyl Hexapeptide-8 in Cosmeceuticals — A Review of Skin Permeability and Efficacy. Int J Mol Sci. 2025;26(12):5722. PMID: 40565185
- Blanes-Mira C, Clemente J, Jodas G, et al. A synthetic hexapeptide (Argireline) with antiwrinkle activity. Int J Cosmet Sci. 2002;24(5):303-310. PMID: 18498523
- Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. Int J Mol Sci. 2018;19(7):1987. PMID: 29986520
- Dou Y, Lee A, Zhu L, Morton J, Ladiges W. The potential of GHK as an anti-aging peptide. Aging Pathobiol Ther. 2020;2(1):58-61. PMID: 35083444
- Kachooeian M, Mousivand Z, Sharifikolouei E, et al. Matrixyl Patch vs Matrixyl Cream: A Comparative In Vivo Investigation of Matrixyl (MTI) Effect on Wound Healing. ACS Omega. 2022;7(28):24695-24704. PMID: 35874243
- Yang F, Zhang X, Wang H, et al. Comprehensive evaluation of the efficacy and safety of a new multi-component anti-aging topical eye cream. Skin Res Technol. 2024;30(7):e13790. PMID: 38932444
- Griffiths TW, Watson REB, Langton AK. Skin ageing and topical rejuvenation strategies. Br J Dermatol. 2023;189(Suppl 1):i17-i23. PMID: 37903073
- Chan LKW, Lee KWA, Lee CH, et al. Cosmeceuticals in photoaging: A review. Skin Res Technol. 2024;30(9):e13730. PMID: 39233460
- Draelos ZD. The science behind skin care: Moisturizers. J Cosmet Dermatol. 2018;17(2):138-144. PMID: 29319217