Pal-AHK

Dosing from the Literature

Published for hair: nothing on Pal-AHK itself. Not published: any trial of it, or a use level from any study or safety review.

Pal-AHK is a topical cosmetic ingredient with no parenteral, oral, or systemic dosing role. The "dosing" question reduces to the formulation-percentage at which Pal-AHK is incorporated into a finished serum, cream, or scalp tonic, and the application frequency the consumer follows.

No trial, label or safety review gives a use level for Pal-AHK. For comparison, CIR's 2018 safety assessment gives typical use concentrations below 10 ppm for palmitoyl tripeptide-1 (Pal-GHK) and related peptides (Johnson et al., 2018), and the 12-week pal-KTTKS trial in 93 women used 3 ppm (Robinson et al., 2005).

What It Is

Pal-AHK is the palmitoylated form of the tripeptide (a chain of 3 amino acids) L-alanyl-L-histidyl-L-lysine (AHK) — three amino acids (Ala–His–Lys) covalently joined to palmitic acid, a sixteen-carbon saturated fatty acid, via an amide bond at the N-terminal alanine. Its calculated molecular weight is approximately 592 daltons. A palmitoyl chain makes a peptide more fat-soluble and has helped other peptides into skin: in hairless-mouse skin, palmitoyl-KTTKS was found in the stratum corneum, epidermis and dermis, while unmodified KTTKS was found in none of them (Choi et al., 2014). No skin-penetration study of Pal-AHK has been published.

The AHK sequence itself was identified by Loren Pickart and colleagues during the same broad program of work that produced the better-known glycyl-L-histidyl-L-lysine (GHK) tripeptide isolated from human plasma in 1973 (PMID 4356974). GHK and AHK differ by a single amino acid at position one — glycine versus alanine — and both share the central histidine and C-terminal lysine that form the copper-binding triangle of the GHK-Cu and AHK-Cu complexes. The biological history of these tripeptides has been driven primarily by the copper complexes: GHK-Cu became one of the most studied "matrikine (a signaling fragment from broken-down skin matrix)" peptides in cosmetic dermatology, and AHK-Cu was characterized in 2007 by Pyo and colleagues at Seoul National University as a stimulator of human dermal papilla cells and ex-vivo human hair follicle elongation (PMID 17703734).

Pal-AHK is a cosmetic-industry derivative of that lineage. Whereas AHK-Cu carries the copper(II) ion that the literature consistently identifies as a key driver of the complex's biological activity, Pal-AHK is the copper-free tripeptide carried instead on a fatty-acid tail. The rationale for the substitution is straightforward: copper-peptide complexes are blue-green, can stain formulations and skin, oxidize ascorbic acid and thiol antioxidants on contact, and create incompatibilities with common cosmetic excipients including silicones, emulsifiers with chelating impurities, and reduced-form vitamins. Palmitoylation removes those handling problems while preserving the AHK amino-acid sequence that suppliers cite as the receptor-binding "address" of the molecule.

The trade-off, which is rarely surfaced clearly in supplier marketing, is that the bulk of the mechanistic and bioactivity evidence cited in support of Pal-AHK was generated using AHK-Cu — the copper-bound form. Whether a copper-free, palmitoyl-conjugated AHK retains the same hair-follicle dermal papilla cell stimulation or the same anti-apoptotic effect as AHK-Cu is an empirical question that has not been answered in the indexed literature. Suppliers typically argue that the AHK sequence is the active pharmacophore and that the lipidated free peptide retains some subset of the receptor-level effects, but independent in-vitro head-to-head comparisons of AHK-Cu versus Pal-AHK at matched concentrations are not available in PubMed-indexed publications. This is the single most important caveat for interpreting cosmetic marketing copy that cites the Pyo 2007 study or the broader copper-peptide body of work as evidence for a Pal-AHK serum.

Within the cosmetic INCI-naming framework, the "palmitoyl tripeptide" names are easy to confuse. Palmitoyl Tripeptide-1 is palmitic acid joined to a glycine–histidine–lysine tripeptide (Pal-GHK), one of the two actives in Matrixyl 3000. Palmitoyl Tripeptide-5 is palmitic acid joined to a lysine–valine tripeptide (Pal-Lys-Val-Lys, sold as Syn-Coll), and the International Cosmetic Ingredient Dictionary lists "palmitoyl tripeptide-3" as a technical name for it, so that name does not belong to Pal-AHK (CIR's 2012 literature review of palmitoyl oligopeptides; Schagen 2017). CosIng, the EU's cosmetic-ingredient register, has no entry named Palmitoyl Tripeptide-3 and none described as a tripeptide of alanine, histidine and lysine, palmitoylated or not (searched October 4, 2026), and none of the palmitoyl tripeptides in CIR's 2012 table is one either. No INCI name for Pal-AHK could be found.

Mechanism of Action

PubMed lists no study of Pal-AHK (searched October 4, 2026). The mechanism claims made for it are borrowed from the one study of the copper-bound AHK-Cu, on cultured human dermal papilla cells and hair follicles (Pyo 2007), and from skin-penetration work on other palmitoyl peptides. The summary below clearly distinguishes what is established for the AHK sequence (in its copper-bound form) from what is claimed but unproven for Pal-AHK specifically.

• Claimed dermal papilla cell stimulation — The central mechanistic claim for the AHK sequence comes from Pyo et al. 2007 (PMID 17703734), in which AHK-Cu²⁺ at picomolar to nanomolar concentrations (10⁻¹² to 10⁻⁹ M) stimulated proliferation of cultured human dermal papilla cells (DPCs) and elongation of ex-vivo human hair follicles in organ culture. Dermal papilla cells are specialized fibroblasts that are important in the formation and growth of hair follicles (Pyo 2007). Only the copper-bound complex was tested; no study has tested whether the copper-free palmitoylated form has the same effect.
• Claimed VEGF / angiogenic signaling — Pickart's review lists increased synthesis of vascular endothelial growth factor (VEGF), a driver of blood-vessel growth, among the effects of GHK and GHK-Cu (Pickart 2008 GHK tissue-remodeling review). Pyo 2007 mentions VEGF only as background on the tripeptide-copper complex in dermal fibroblasts; its reported results for AHK-Cu include no VEGF measurement, and no study has measured VEGF with Pal-AHK.
• Claimed perifollicular dermal sheath / fibroblast (a cell that builds collagen) activation — Reviews of GHK and GHK-Cu report increased fibroblast proliferation and collagen and glycosaminoglycan synthesis (Pickart 2008; Pickart & Margolina 2018). No study has tested Pal-AHK on skin fibroblasts or collagen; applying these findings to it is extrapolation.
• Anti-apoptotic claim — Pyo 2007 reported fewer apoptotic dermal papilla cells (programmed cell death) with AHK-Cu, but states the fall was not statistically significant. At 10⁻⁹ M the ratio of Bcl-2 to Bax rose and cleaved caspase-3 and PARP fell, which the authors proposed as a way AHK-Cu might prevent the cells' death. No study has looked at apoptosis with Pal-AHK.
• Palmitoyl chain and skin penetration — Palmitoylation has helped other peptides into skin, but it has never been measured for Pal-AHK. Schagen 2017 (Cosmetics 4:16) reports that unmodified carnosine (β-Ala-His) does not penetrate beyond the first layer of the stratum corneum, while palmitoyl-β-Ala-His diffuses into the stratum corneum, epidermis and dermis, with no systemic activity observed. In hairless-mouse skin, palmitoyl-KTTKS was found in the stratum corneum, epidermis and dermis, unmodified KTTKS in none of them, and neither crossed the full thickness of the skin (Choi 2014; PMID 25143811).
• Signal-peptide framework — In the cosmetic-peptide taxonomy of Lupo & Cole 2007 (PMID 18045359), peptides are classified as signal peptides (mimicking matrix-degradation fragments to trigger collagen and elastin synthesis), neurotransmitter-affecting peptides (botulinum-toxin-mimetic), or carrier peptides (delivering trace metals such as copper). Pal-AHK is positioned by suppliers as a signal peptide; no study has tested whether it acts as one. The carrier-peptide identity (delivering Cu²⁺) that defines AHK-Cu is, by construction, absent in the non-copper lipidated form.
• Caveat: copper's share is untested — Pyo 2007 tested only the copper complex, so its results cannot separate what the AHK peptide does from what copper does. For the related GHK, Pickart & Margolina 2018 (PMID 29986520) write that the copper hypothesis "doesn't explain the gene modulating effects of GHK-Cu" and that GHK "with and without copper" affects a large number of genes. No such data exist for AHK, with or without copper.

What the Research Shows

PubMed lists no study of Pal-AHK (searched October 4, 2026). The mechanistic and efficacy claims that appear in supplier and brand marketing materials are extrapolated from three adjacent bodies of work: (1) the one AHK-Cu hair-follicle study (Pyo 2007); (2) the GHK / GHK-Cu dermatology and tissue-remodeling literature reviewed by Pickart and Margolina; and (3) the general cosmetic-peptide skin-penetration and signal-peptide literature reviewed by Schagen, Lupo & Cole, and others.

• Pyo 2007 — AHK-Cu on human hair follicles (PMID 17703734) — The only study of the AHK sequence on hair that PubMed lists. Cultured human dermal papilla cells were exposed to L-alanyl-L-histidyl-L-lysine-Cu²⁺ at concentrations from 10⁻¹² to 10⁻⁹ M; proliferation rose, and there were fewer apoptotic cells, though that fall was not statistically significant. Ex-vivo human hair-follicle organ cultures showed increased follicle elongation. The mechanistic readouts were apoptosis markers: at 10⁻⁹ M the Bcl-2/Bax ratio rose and cleaved caspase-3 and PARP fell; the reported results include no VEGF or TGF-β1 measurement. Limitation: this is in-vitro / ex-vivo only; the agent tested was the copper-bound complex, not Pal-AHK; no clinical hair-count or hair-density data; single laboratory.
• Pickart 2008 — GHK and tissue remodeling (J Biomater Sci Polym Ed) — Comprehensive review of the GHK / GHK-Cu literature with brief reference to the broader tripeptide-copper family. Describes wound healing, hair-transplant survival improvements, and gene-expression effects. Establishes the framework within which the AHK literature is interpreted but does not provide independent Pal-AHK evidence.
• Pickart & Margolina 2018 — GHK-Cu transcriptomics (PMID 29986520) — Transcriptome analysis of GHK and GHK-Cu effects on human gene expression. Documents broad effects on wound-healing, anti-inflammatory, and antioxidant gene programs. Frequently cited by Pal-AHK marketing as evidence for "gene modulation" claims; the underlying data is for GHK / GHK-Cu, not for AHK or Pal-AHK.
• Pickart 2012 — GHK-Cu and oxidative stress / cognitive aging (PMID 22666519) — Review of the human tripeptide GHK-Cu in prevention of oxidative stress and degenerative conditions of aging. Provides historical context for the tripeptide-copper class; not directly applicable to Pal-AHK.
• Lupo & Cole 2007 — Cosmeceutical peptides review (PMID 18045359) — Categorizes cosmetic peptides into signal, neurotransmitter-affecting, and carrier classes. Frames the rationale for palmitoylation as a delivery strategy. Does not directly evaluate Pal-AHK.
• Schagen 2017 — Topical peptide treatments (Cosmetics 4:16) — Open-access review of cosmetic peptides covering pal-KTTKS, palmitoyl tripeptide-1 / -3 / -5, palmitoyl-β-Ala-His, and others. Describes a 60-volunteer 84-day study in which palmitoyl tripeptide-3/5 outperformed placebo and pal-KTTKS for anti-wrinkle endpoints. Does not include data specific to a non-copper Pal-AHK product.
• Robinson 2005 — pal-KTTKS RCT (PMID 18492182) — A 12-week double-blind placebo-controlled split-face study of 93 women applying 3 ppm pal-KTTKS in moisturizer. Significant improvement in fine lines and wrinkles versus moisturizer alone. Cited here as the methodological template for what a real palmitoyl-peptide cosmetic RCT looks like — a template that has not been applied to non-copper Pal-AHK.
• Choi 2014 — KTTKS / pal-KTTKS skin permeation (PMID 25143811) — Dermal stability and in-vitro skin permeation comparison of free KTTKS versus palmitoyl-KTTKS. Confirms that palmitoylation increases skin permeation and dermal stability of the parent peptide. Mechanistically informative for the palmitoyl peptide class as a whole.
• Cosmetic peptide reviews 2020–2024 — More recent reviews of the cosmetic peptide field (PMID 34957891 anti-ageing peptide review; PMID 34451799 synthetic peptides in cosmetics for sensitive skin) catalogue the palmitoyl tripeptide family on INCI lists of marketed products; the non-copper Pal-AHK does not appear as a separately reviewed entity in any major peer-reviewed cosmetic-dermatology review through 2024.
• Manufacturer / supplier in-house data — Several cosmetic raw-material suppliers provide in-house in-vitro proliferation assays, ex-vivo skin equivalent collagen-synthesis assays, or finished-product hair-density photometric studies for products containing Pal-AHK. These data are not peer-reviewed; they are marketing literature, not clinical evidence.

Human Data

There are essentially zero peer-reviewed clinical randomized controlled trials of non-copper Pal-AHK as a stand-alone topical agent in the indexed literature. The published "human data" attached to Pal-AHK marketing falls into three categories, none of which constitute clinical evidence in the regulatory sense applied to drug development:

• Ex-vivo human tissue data (AHK-Cu, not Pal-AHK) — Pyo et al. 2007 (PMID 17703734) used cultured human dermal papilla cells and ex-vivo human hair-follicle organ cultures from scalp biopsy explants. This is human-derived tissue, but is not a clinical trial; the agent was AHK-Cu²⁺, not the lipidated free peptide.
• Adjacent compound clinical trials — Robinson et al. 2005 (PMID 18492182) is the closest published methodological analog: a 12-week double-blind placebo-controlled split-face RCT of pal-KTTKS in moisturizer in 93 women, demonstrating quantitative wrinkle-reduction superiority versus vehicle. Schagen 2017 cites a 60-volunteer 84-day controlled study of palmitoyl tripeptide-3/5 in which the lipidated tripeptide outperformed placebo and pal-KTTKS. Neither study tested Pal-AHK.
• Manufacturer-funded finished-product hair-growth studies — Several cosmetic brands have commissioned uncontrolled or single-arm photometric hair-density and hair-count studies on multi-ingredient hair serums containing Pal-AHK alongside other actives (caffeine, niacinamide, biotin, redensyl-class compounds, copper peptides, plant extracts). These studies generally are not registered on ClinicalTrials.gov, are not published in peer-reviewed indexed journals, and cannot isolate the contribution of Pal-AHK from the rest of the formulation. They function as marketing collateral, not as evidence of Pal-AHK efficacy.

For category context, the broader topical-peptide RCT base that exists for compounds in the same family — pal-KTTKS (Robinson 2005, PMID 18492182), palmitoyl tripeptide-3/5 (Schagen 2017 review), GHK-Cu in wound-healing and hair-transplant adjunct contexts (Pickart 2008 J Biomater Sci Polym Ed), and the broader cosmetic-peptide reviews by Lupo & Cole 2007 (PMID 18045359), the synthetic-peptide cosmetics review (PMID 34451799), and the Pickart & Margolina 2018 GHK-Cu transcriptomics paper (PMID 29986520) — illustrates that well-designed placebo-controlled topical-peptide RCTs are feasible, are sometimes done, and typically yield modest but statistically detectable wrinkle, firmness, or hair-density improvements when the underlying active and vehicle are well-characterized. The absence of such a study for Pal-AHK is notable. It is not evidence that Pal-AHK does not work; it is evidence that the manufacturers selling it have not invested in the kind of trial that would tell us whether it does.

From the regulatory perspective, this evidence gap is unsurprising. Pal-AHK is sold as a cosmetic ingredient, not as a drug, and the U.S. cosmetic regulatory framework does not require demonstration of efficacy. A cosmetic may claim to change how skin or hair looks; FDA treats a claim that a product will restore hair growth, regenerate cells or otherwise affect the structure or function of the body as a drug claim (FDA, "Is It a Cosmetic, a Drug, or Both?"). The economic incentive to invest in a peer-reviewed RCT is therefore minimal, and the resulting evidence base is what it is — adequate for cosmetic marketing, inadequate for clinical claims.

Reconstitution & Storage

Pal-AHK is sold as a cosmetic ingredient and is not reconstituted the way injectable peptides are. No study or safety review gives storage or handling conditions for it.

→ Calculator — vial-to-syringe math

Side Effects & Risks

No safety data on Pal-AHK itself have been published, so what is known comes from other palmitoyl peptides. CIR's expert panel concluded in 2018 that palmitoyl tripeptide-1 (Pal-GHK) and related peptides are safe in cosmetics as used, at typical concentrations below 10 ppm, citing negative safety test data (Johnson et al., 2018); Pal-AHK was not part of that review.

• Contact sensitization — No sensitization data exist for Pal-AHK. CIR's 2012 literature review of palmitoyl oligopeptides found no published skin irritation or sensitization studies of palmitoyl peptides; it noted that the 12-week pal-KTTKS trial in 93 women reported no skin irritation (Robinson et al., 2005).
• Lack of systemic safety data — No toxicology data on Pal-AHK, by any route, have been published, and CIR's 2012 review found no published acute, repeated-dose, genotoxicity or carcinogenicity data on palmitoyl oligopeptides. Off-label systemic use is not supported by any safety evidence.
• No documented drug-drug interactions — No interaction study of Pal-AHK has been published.
• Pregnancy and lactation — No pregnancy or lactation data exist for Pal-AHK, and CIR's 2012 review found no published reproductive or developmental toxicity data on palmitoyl oligopeptides.
• Pediatric use — No study of Pal-AHK, in children or adults, has been published.
• WADA status — Topical cosmetic Pal-AHK is not specifically listed on the World Anti-Doping Agency Prohibited List. The 2026 Prohibited List does not name it or the cosmetic peptide class (World Anti-Doping Agency, 2026).

Bloodwork & Monitoring

Pal-AHK is a topical cosmetic ingredient. No trial, label or guideline sets monitoring for it, and no study of it has measured anything in people.

Commonly Stacked With

Pal-AHK is sold as one ingredient of multi-ingredient hair serums and skin creams. No study has tested it with any other ingredient; the pairings below are the ones this page describes in such products.

Stacking this? Read the receipt →

→ Calculator — vial-to-syringe math

Legal Status

Related Compounds

Lipidated tripeptide cousins in the palmitoyl family:

Next Steps

References

1. Pyo HK, Yoo HG, Won CH, Lee SH, Kang YJ, Eun HC, Cho KH, Kim KH. The effect of tripeptide-copper complex on human hair growth in vitro. Arch Pharm Res. 2007;30(7):834-839. doi:10.1007/BF02978833. PMID: 17703734. (The single most-cited primary study for the AHK sequence in any hair-growth context. AHK-Cu²⁺ at 10⁻¹² to 10⁻⁹ M stimulated proliferation of cultured human dermal papilla cells, reduced apoptosis, increased VEGF expression, and elongated ex-vivo human hair follicles. The agent tested was the copper-bound complex, not Pal-AHK.)
2. Pickart L, Thaler MM. A synthetic tripeptide which increases survival of normal liver cells, and stimulates growth in hepatoma cells. Biochem Biophys Res Commun. 1973;54(2):562-566. doi:10.1016/0006-291x(73)91459-9. PMID: 4356974. (The original Pickart hepatocyte tripeptide paper that launched the GHK / AHK tripeptide-copper field.)
3. 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. doi:10.3390/ijms19071987. PMID: 29986520. (Comprehensive 2018 transcriptomic review of GHK and GHK-Cu effects on human gene expression. Frequently cited by Pal-AHK marketing as evidence for "gene modulation" claims; the underlying data is for GHK / GHK-Cu, not for AHK or Pal-AHK.)
4. Pickart L, Vasquez-Soltero JM, Margolina A. The human tripeptide GHK-Cu in prevention of oxidative stress and degenerative conditions of aging: implications for cognitive health. Biomed Res Int. 2012;2012:324832. doi:10.1155/2012/324832. PMID: 22666519. (Review of the human tripeptide GHK-Cu in prevention of oxidative stress and degenerative conditions of aging; provides historical context for the tripeptide-copper class.)
5. Pickart L. The human tri-peptide GHK and tissue remodeling. J Biomater Sci Polym Ed. 2008;19(8):969-988. doi:10.1163/156856208784909435. PMID: 18644225. (Comprehensive review of the GHK / GHK-Cu literature including wound healing, hair-transplant survival, and gene-expression effects. Establishes the framework within which the AHK literature is interpreted.)
6. Lupo MP, Cole AL. Cosmeceutical peptides. Dermatol Ther. 2007;20(5):343-349. doi:10.1111/j.1529-8019.2007.00148.x. PMID: 18045359. (Categorizes cosmetic peptides into signal, neurotransmitter-affecting, and carrier classes. Frames the rationale for palmitoylation as a delivery strategy. Foundational cosmetic-peptide review.)
7. Schagen SK. Topical Peptide Treatments with Effective Anti-Aging Results. Cosmetics. 2017;4(2):16. doi:10.3390/cosmetics4020016. (Open-access review covering pal-KTTKS, palmitoyl tripeptide-1 / -3 / -5, palmitoyl-β-Ala-His, and others, with clinical-study citations and mechanistic discussion of palmitoyl-peptide skin penetration.)
8. Robinson LR, Fitzgerald NC, Doughty DG, Dawes NC, Berge CA, Bissett DL. Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin. Int J Cosmet Sci. 2005;27(3):155-160. doi:10.1111/j.1467-2494.2005.00261.x. PMID: 18492182. (12-week double-blind placebo-controlled split-face RCT in 93 women applying 3 ppm pal-KTTKS in moisturizer; significant improvement in fine lines and wrinkles versus moisturizer alone. The methodological template for what a real palmitoyl-peptide cosmetic RCT looks like.)
9. Choi YL, Park EJ, Kim E, Na DH, Shin YH. Dermal Stability and In Vitro Skin Permeation of Collagen Pentapeptides (KTTKS and palmitoyl-KTTKS). Biomol Ther (Seoul). 2014;22(4):321-327. doi:10.4062/biomolther.2014.053. PMID: 25143811. (Confirms that palmitoylation increases skin permeation and dermal stability of the parent peptide; mechanistically informative for the palmitoyl-peptide class as a whole.)
10. Resende DISP, Ferreira MS, Sousa-Lobo JM, Sousa E, Almeida IF. Usage of Synthetic Peptides in Cosmetics for Sensitive Skin. Pharmaceuticals (Basel). 2021;14(8):702. doi:10.3390/ph14080702. PMID: 34451799. (Analysis of 88 facial cosmetics for sensitive skin, showing that palmitoyl tripeptide-8, palmitoyl tripeptide-5, palmitoyl tetrapeptide-7, and palmitoyl oligopeptide are commonly used in marketed products. Useful context for where the palmitoyl-tripeptide family sits in the contemporary cosmetic ingredient landscape.)
11. Errante F, Ledwoń P, Latajka R, Rovero P, Papini AM. Cosmeceutical Peptides in the Framework of Sustainable Wellness Economy. Front Chem. 2020;8:572923. doi:10.3389/fchem.2020.572923. (Modern review of cosmeceutical peptides including the GHK / AHK family in the context of cosmetic regulatory frameworks and sustainability; cites Lupo & Cole and the broader signal-peptide literature.)
12. Ferreira MS, Magalhães MC, Sousa-Lobo JM, Almeida IF. Trending Anti-Aging Peptides. Cosmetics. 2020;7(4):91. doi:10.3390/cosmetics7040091. (Open-access review of the cosmetic peptide field; catalogues the palmitoyl tripeptide family on INCI lists of marketed products.)
13. Gorouhi F, Maibach HI. Role of topical peptides in preventing or treating aged skin. Int J Cosmet Sci. 2009;31(5):327-345. doi:10.1111/j.1468-2494.2009.00490.x. PMID: 19570099. (Foundational review of topical peptides in aging-skin applications; covers GHK-Cu, pal-KTTKS, palmitoyl-Gly-His-Lys, and related compounds with mechanism and clinical-evidence discussion.)
14. Aldag C, Nogueira Teixeira D, Leventhal PS. Skin rejuvenation using cosmetic products containing growth factors, cytokines, and matrikines: a review of the literature. Clin Cosmet Investig Dermatol. 2016;9:411-419. doi:10.2147/CCID.S116158. PMID: 27877059. (Cosmetic-dermatology review of growth-factor and matrikine peptide products with discussion of palmitoyl peptide class.)
15. Cosmetic Ingredient Review Expert Panel. Safety Assessment of Palmitoyl Oligopeptides as Used in Cosmetics. CIR Final Report. 2012. Available at cir-safety.org. (Industry-standard safety assessment of the palmitoyl oligopeptide class, including discussion of skin penetration, irritation, sensitization, and acute and repeated-dose toxicology data gaps. Pal-AHK falls within the scope of this class assessment.)
16. Lima TN, Moraes CAP. Bioactive Peptides: Applications and Relevance for Cosmeceuticals. Cosmetics. 2018;5(1):21. doi:10.3390/cosmetics5010021. (Open-access review of bioactive peptides in cosmeceutical applications; covers signal-peptide, carrier-peptide, and neurotransmitter-affecting peptide classes.)
17. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (503A categories list), versions updated April 15, April 22 and May 14, 2026. fda.gov/media/94155/download. Read October 3, 2026. (Notice that 12 peptides would leave Category 2 because their nominations were withdrawn; their removal; GHK-Cu, except injectable, back in Category 1.)
18. Johnson W Jr, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler DC, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Gill LJ, Heldreth B. Safety Assessment of Tripeptide-1, Hexapeptide-12, Their Metal Salts and Fatty Acyl Derivatives, and Palmitoyl Tetrapeptide-7 as Used in Cosmetics. Int J Toxicol. 2018;37(3 suppl):90S-102S. doi:10.1177/1091581818807863. (Cosmetic Ingredient Review final report: typical use concentrations of these ingredients are below 10 ppm, and the Expert Panel concluded they are safe in cosmetics in the present practices of use and concentration. Pal-AHK is not among them.)

Related Research

• AHK-CuCopper Tripeptide (Hair)
• GHK-CuCopper Tripeptide, Skin & Connective Tissue
• ArgirelineSNAP-25 Mimetic
• Decapeptide-12Tyrosinase Inhibitor
• FDA TrackerPCAC voted on 7 of the 12 peptides on July 23–24, 2026; FDA plans a PCAC review of the other 5 before the end of February 2027.