AHK-Cu

AHK, known by its cosmetic ingredient name Tripeptide-3, is a short synthetic peptide made of three amino acids, L-alanine, L-histidine, and L-lysine (Ala-His-Lys). It belongs to the family of copper-binding signal peptides, small sequences whose histidine and lysine residues chelate copper(II) ions to form a biologically active metal-peptide complex. In this respect AHK is a close relative of the much-studied peptide GHK (glycyl-histidyl-lysine), differing by a single amino acid, and it shares GHK's central property of ferrying copper to cells and acting as a regenerative signal ^[2].

The copper-binding nature of AHK is central to how it is used. On its own the bare peptide is essentially a copper carrier; its documented bioactivity is realized as the copper complex AHK-Cu (L-alanyl-L-histidyl-L-lysine-Cu2+). In laboratory studies this complex stimulated the elongation of human hair follicles grown outside the body and promoted the proliferation of dermal papilla cells, the specialized cells at the base of the follicle that orchestrate hair growth ^[1]. Tripeptide-copper complexes as a class have long been recognized as growth-factor-like molecules that raise vascular endothelial growth factor, support collagen production, and accelerate the repair of skin and other tissues ^[2][3][4].

AHK (Tripeptide-3) is used primarily as a cosmetic and hair-care active rather than as a medicine. It appears in serums, hair tonics, and scalp treatments, typically supplied as a powder for formulation or already combined with copper. Regulatorily it is treated as a cosmetic ingredient, not an approved drug, and much of the human-relevant evidence comes from cell-culture and ex vivo follicle studies together with the broader literature on copper peptides in skin regeneration ^[1][2]. Its appeal lies in offering the well-regarded copper-peptide biology of GHK in a distinct, alanine-containing sequence.

As a topical cosmetic peptide it is generally well tolerated, with possible local irritation, redness, or contact sensitivity. Copper peptides can occasionally irritate sensitive skin. There is little data on internal use, which is not the intended route.

AHK-Cu is the copper complex of the tripeptide alanine-histidine-lysine, a member of the copper-peptide field that grew out of the discovery of the human plasma factor GHK and its copper complex in the 1970s. Its most cited scientific milestone is a 2007 study by Pyo and colleagues at Seoul National University, who showed that AHK-Cu, at picomolar-to-nanomolar concentrations, lengthened human hair follicles grown ex vivo and stimulated the dermal papilla cells at the root of the follicle while reducing markers of programmed cell death.

Beyond that specific hair work, its rationale draws on the broader, well-documented actions of copper tripeptides on collagen synthesis, angiogenesis and wound healing. Formal development history for AHK-Cu itself is limited; it is used chiefly as a cosmetic ingredient rather than as an approved drug, and much of what is claimed for it is extrapolated from the more heavily studied GHK-Cu.

AHK-Cu is a favorite among copper peptides for hair density and scalp and skin renewal, often described as a potent cousin of the famous GHK-Cu, and its reputation rests on a genuinely appealing dual identity as both a cell-signaling peptide and a delivery vehicle for bioavailable copper. The laboratory evidence that it lengthens hair follicles and multiplies dermal papilla cells while shielding them from apoptosis gives it real scientific grounding for cosmetic use, and copper's established role as a cofactor for collagen-crosslinking and blood-vessel-forming enzymes reinforces the story.

It is fair to note that the direct human evidence is thin, resting largely on cell and ex vivo studies rather than controlled clinical trials, and that many benefits are inferred from related copper tripeptides. As a topical cosmetic ingredient with a plausible mechanism, it is popular and well-liked, if not clinically proven.