Copper Tripeptide-3
AHK-Cu — evidence, the "hair growth" claim trap & status

Class: peptide
INCI name: Copper Tripeptide-3
Synonyms: AHK-Cu
L-alanyl-L-histidyl-L-lysine copper (Ala-His-Lys + Cu²⁺)
"Copper Tripeptide-3"
a copper peptide "for hair." INCI: as named. High-volume search: "AHK-Cu vs GHK-Cu."
Function tags: hair appearance (cosmetic)
scalp
(reference:) dermal papilla / anagen-phase biology
Overall evidence grade: C
WADA prohibited: no
Last updated: 2026-07-13

In brief: AHK-Cu is a copper-binding tripeptide engineered for hair (whereas GHK-Cu targets skin). Its evidence is essentially one foundational ex-vivo/in-vitro study (Pyo 2007) showing it stimulates hair-follicle elongation and dermal-papilla-cell proliferation in the lab — but there is no robust human trial showing a topical AHK-Cu serum actually increases hair density in people, and "hair growth" is a medicinal claim (the space occupied by drugs like minoxidil and finasteride). It is a cosmetic ingredient; appearance claims only.

## Identity a synthetic **copper-binding tripeptide** (3 amino acids + Cu²⁺; < 40 aa → peptide), structurally like **GHK-Cu (#26)** but with **alanine instead of glycine** at position 1. Unlike GHK-Cu, it does **not occur naturally** in the body — it was **engineered specifically for hair/scalp applications** (GHK-Cu is skin-focused; AHK-Cu is hair-focused). ## Development & history - Designed as a synthetic copper-peptide analog optimised for **hair-follicle activity**. The foundational (and essentially only pivotal) study is **Pyo HK et al., *Archives of Pharmacal Research*, 2007** (PMID 17703734), which established its effects on cultured follicles and dermal papilla cells.
- Commercialised in **hair/scalp serums**, frequently **combined with GHK-Cu** (skin/anti-inflammatory) for a multi-pathway "copper peptide" product. Only ever a cosmetic/research ingredient — never a drug. ## Mechanism (as proposed) a copper-binding tripeptide that, in vitro/ex vivo, stimulates **dermal papilla cell** proliferation and reduces their apoptosis (↑Bcl-2/Bax, ↓caspase-3), raises **VEGF** (follicular blood supply), lowers **TGF-β1** (delaying catagen), and engages **Wnt/β-catenin** (the anagen switch). Most of this is lab-based; in-vivo topical relevance is constrained by skin/scalp penetration, and the dose-response is **biphasic** ("more is not better").

## Related reading

What copper peptides are, and how the hair-focused AHK-Cu differs from skin-focused GHK-Cu, in [what are copper peptides](/learn/what-are-copper-peptides). Where copper peptides rank among the cosmetic peptides by evidence: [cosmetic peptides ranked by evidence](/learn/best-peptides-for-skin). How AHK-Cu's in-vitro evidence stacks up against the rest of a hair serum's ingredients — and where "growth" quietly becomes "support": [do hair growth serums actually work?](/learn/do-hair-growth-serums-work).

Evidence grades by outcome:
outcome: Hair-follicle elongation / dermal-papilla-cell proliferation (in vitro / ex vivo)
grade: C
base: Pyo 2007 (Arch Pharm Res) — cultured human follicles + DPCs
effect: Genuine stimulation; anti-apoptotic (↑Bcl-2/Bax); ↑VEGF, ↓TGF-β1
caveat: Ex vivo / in vitro only; a single foundational study; a lab effect is not a clinical effect
outcome: Topical serum increasing hair density in people (the marketed use)
grade: D
base: No robust human RCT of an AHK-Cu serum
effect: Not demonstrated
caveat: The lab signal doesn't establish a clinical serum effect; penetration to the dermal papilla from a serum is doubtful (enhanced-delivery methods like microneedling perform better)
outcome: "Regrows hair / treats hair loss"
grade: F
base: None (cosmetic)
effect: Not demonstrated
caveat: Not shown for a cosmetic serum — and it is a drug claim (cf. minoxidil / finasteride)
outcome: Safety (topical)
base: Broad cosmetic use
effect: Well tolerated; hormone-neutral
caveat: No hormonal effects (unlike finasteride); suitable for both sexes; long-term data lacking

Legal status:
region: EU
status: a cosmetic ingredient in topical hair products (EU Regulatio
note: a cosmetic ingredient in topical hair products (EU Regulation (EC) 1223/2009; US cosmetic law). But note: hair-growth / anti-hair-loss claims are medicinal — a product making them would be treated as an (unlicensed) drug, not a cosmetic. No injectable lane. Sellable as a cosmetic only with appearance-level claims.

Cosmetic claims:
allowed: for **fuller-, thicker-looking** hair
healthier-**looking** hair and scalp.
forbidden: grows / regrows hair
treats / prevents hair loss
stimulates hair follicles
increases hair density / count
extends the anagen phase

Note: Cosmetic copper-carrier peptide — for hair (vs GHK-Cu's skin focus). Two honest points define this page: (1) its evidence is essentially one ex-vivo/in-vitro study, not a human trial; and (2) "hair growth" claims are medicinal (drug territory, like minoxidil) — a cosmetic can only speak to appearance.

Sources:
Pyo HK, Yoo HG, Won CH, et al. The effect of tripeptide-copper complex on human hair growth in vitro. Arch Pharm Res. 2007;30(7):834–839. (PMID 17703734) — the foundational ex-vivo/in-vitro study.
Copper-peptide hair reviews (2025–2026) — noting enhanced-delivery (microneedling) results and the lab-vs-clinical gap.
Pickart L, et al. — GHK / copper-peptide grounding (for the class).