Skin & hair.
Topical evidence is stronger than systemic for this class. Pigmentation peptides carry distinct safety considerations.
How this class moves the outcome.
Collagen / elastin gene expression
GHK-Cu drives dermal matrix gene expression in fibroblast culture and human skin biopsies — the best-supported topical mechanism here.
Melanocortin receptor agonism
Melanotan-1 / 2 stimulate MC1R-driven melanogenesis. Off-target receptor activity drives most documented side effects.
Ranked by human-evidence strength.
- 01
GHK-Cu
Copper Tripeptide-1Naturally occurring copper-binding tripeptide. Topical use studied for skin remodelling; injectable use is anecdotal.
Copper-binding tripeptidet½ Short (minutes, plasma)Human observational - 02
Melanotan II
MT-IICyclic α-MSH analogue, the parent of bremelanotide. Unapproved; significant adverse-event profile.
α-MSH analogue (cyclic)t½ ~33 minPreclinical only - 03
Melanotan I
AfamelanotideLinear α-MSH analogue (afamelanotide), approved as Scenesse for erythropoietic protoporphyria.
α-MSH analoguet½ ~30 min (free); implant releases over monthsHuman RCT
What the human data actually shows.
Each bar is the proportion of candidates on this brief at that evidence tier. RCT first, observational second, preclinical and anecdotal labeled and never inflated.
See full methodology →Indexed human trials and reviews driving the candidate rankings above. Sorted by study type, then recency.
- moderateDorr RT, Lines R, Levine N, et al.
Daily SC melanotan-II produced dose-dependent skin darkening (reflectance measurements) in human volunteers; nausea and flushing common at higher doses.
Observationaln=281996unreviewed - moderatePickart L, Margolina APreclinical2018unreviewed
- moderatePickart L, Margolina A
GHK-Cu upregulates collagen, glycosaminoglycans, and antioxidant enzymes in human dermal fibroblasts; clinical topical studies show improved skin density and reduced photodamage.
Preclinical2015unreviewed - moderate
Where this class can hurt you.
- Melanotan products are linked to documented melanocytic changes and GI / cardiovascular effects.
- Topical product quality varies dramatically; concentration and vehicle materially affect outcome.
- Pigmentation is not photoprotection — UV exposure risk is unchanged.
- Pigmentation peptides have documented adverse events — not a cosmetic-grade safety profile.
- Topical bioavailability data is fragmented across vehicle formulations.
Decide between candidates.
Put the top 3 candidates side by side.
Mechanism · half-life · routes · evidence tier · safety signals. A decision matrix, not a leaderboard.
Current scientific consensus.
- Topical GHK-Cu for skin density
- Melanotan for pigmentation (effect, not safety)
- Melanotan as photoprotection
- Systemic peptide use replacing topical dermatology
- Long-term melanocyte safety with repeated use
"Topical wins are real. Systemic pigmentation use is the highest-risk peptide category for cosmetic intent."
Where this is heading.
Topical wins are real. Systemic pigmentation use is the highest-risk peptide category for cosmetic intent.
We re-grade this brief quarterly. Confidence and outcome grades shift as new RCTs publish, safety data accumulates, and replication efforts read out. Changes are logged publicly on the evidence changelog.
Matched protocol templates.
Matching templates…