Palmitoyl Tripeptide-38

GHK-Cu is the copper(II) complex of GHK, a naturally occurring human tripeptide (glycyl-L-histidyl-L-lysine) found in blood plasma, saliva and urine, whose levels decline with age. It is researched and widely used in cosmetic skincare for skin regeneration, wound healing, collagen support and anti-aging. It is not an FDA-approved drug; it appears in over-the-counter cosmetics and as a research or compounded peptide, with most human evidence coming from small topical-skincare studies.

Matrixyl is the trade name (Sederma) for palmitoyl pentapeptide-4, also written Pal-KTTKS, a collagen-fragment peptide attached to a fatty acid so it can cross skin. Unlike Botox-mimic peptides, it does not touch muscle: it signals skin cells to rebuild collagen, so it is aimed at fine lines, firmness and skin texture rather than expression wrinkles. It is a cosmetic ingredient with one of the better-documented topical studies in the peptide space, though far short of drug-grade proof.

Matrixyl 3000 is Sederma's follow-up to the original Matrixyl, a fixed pair of two fatty-acid-tagged peptides: palmitoyl tripeptide-1 (Pal-GHK) and palmitoyl tetrapeptide-7 (Pal-GQPR). The idea is a one-two punch: one peptide tells skin to rebuild collagen, the other calms the low-grade inflammation that wears collagen down. It is a cosmetic ingredient aimed at firmness, fine lines and aging skin, with supportive but mostly company-generated evidence.

AHK-Cu is a synthetic copper-bound tripeptide, alanine-histidine-lysine complexed with a copper ion, engineered mainly for hair and scalp products. It is the lesser-known sibling of the naturally occurring GHK-Cu copper peptide, designed in the lab specifically to push hair follicles to keep growing. It is a cosmetic and research ingredient, not an approved hair-loss drug, and its evidence is essentially limited to one notable lab study.

Acetyl tetrapeptide-5 is a short synthetic peptide sold by Lipotec (now Lubrizol) as Eyeseryl, made for eye creams that target under-eye puffiness. The pitch is that it reduces fluid leaking into the tissue under the eyes. It is a cosmetic ingredient, and nearly all of the human data comes from the company that sells it.

Hexapeptide-9 is a collagen-inspired signaling peptide sold as Collaxyl (originally from Vincience, now Ashland) for anti-wrinkle and firming skincare. The idea is that a small repeat of a collagen sequence nudges skin cells to rebuild the junction between the outer and inner skin. It is a cosmetic ingredient, and the evidence for the original peptide is mostly old, small and company-run, although a 2025 trial on a modified cyclic version is more interesting.