GHK-Cu
Also known as copper tripeptide-1, copper peptide
The peptide with the most credible cosmetic case. Decent mechanistic work, reasonable small trials, and it is applied to the skin rather than injected.
$20–70 per bottle.
How it works
A naturally occurring copper-binding tripeptide that declines with age. It signals fibroblasts to increase collagen, elastin and glycosaminoglycan production, modulates matrix metalloproteinases, and has antioxidant and wound-healing activity. Copper is a required cofactor for lysyl oxidase, which crosslinks collagen.
How it's used
Used topically at roughly 1–3% in a serum, usually at night. It does not play well with strong acids or direct vitamin C, which can strip the copper from the complex — separate them by routine or by time of day. Injected and scalp-mesotherapy uses exist but are not well evidenced.
Trade-offs
In favour
- Applied topically, so systemic risk is minimal
- Reasonable evidence for firmness, fine lines and wound healing
- Well tolerated on most skin
- Pairs well with a retinoid used on alternate nights
Against
- Effect size is modest next to a retinoid
- Blue-green colour can stain and looks alarming in the bottle
- Formulation quality varies enormously
- Scalp and injectable claims outrun the evidence
Risks and side effects
- Contact irritation, uncommon
- Copper overload is not a realistic concern from topical use at cosmetic concentrations
- Do not layer directly with L-ascorbic acid or strong acids
How good is the evidence?
Several small human trials plus solid mechanistic work support topical use for skin quality. Evidence remains smaller and lower quality than for retinoids.
Sources
Sources point to guideline bodies and literature searches rather than single papers, so they stay accurate as the evidence moves.