Home / Categories / Dermal & cosmetic
Skin, hair, pigmentation.
The one category where the evidence is decent and the products often are not.
4 compounds tracked in this category
Free, no obligation
Every inquiry gets a real answer from a person. If what you're asking about isn't supported by evidence, we'll say so.
In theory, this class is designed to tell your skin to behave younger, signalling fibroblasts to produce more collagen, delivering copper as an enzyme cofactor, interfering with the signalling behind expression lines, or blocking the enzymes that break collagen down. Because skin is accessible and biopsiable, this is the one category where the theory has been properly tested, and it largely works, modestly.
Unmarked, FDA approved° legal over the counter† under FDA review, not yet permitted* not FDA approved‡ documented safety concern
| Compound | What is known |
|---|---|
| Matrixyl (pal-KTTKS)° | Legal cosmetic ingredient. A 12-week double-blind split-face trial in 93 women, the strongest topical peptide evidence available. |
| SNAP-8 / Argireline° | Legal cosmetic ingredients with moderate human evidence. Real but modest effect on expression lines. Not topical Botox. |
| AHK-Cu° | Cosmetic ingredient. Less studied than GHK-Cu. |
| Melanotan I / II‡ | Off Category 2, advisory review pending before February 2027. No established human efficacy data. No established efficacy, and documented adverse events including pigmented lesion changes and priapism. |
The science behind this category
Skin is accessible. You can apply a compound, take a biopsy, and measure collagen directly. Which means real controlled trials are affordable and practical here in a way they are not for systemic compounds. That is why this category has the best evidence base on the site despite attracting the least attention.
Cosmetic peptides divide into signal peptides, which tell fibroblasts to produce more collagen (Matrixyl and the palmitoyl tripeptides). Carrier peptides, which deliver trace metals that act as enzyme cofactors (GHK-Cu, AHK-Cu). Neurotransmitter-inhibiting peptides, which interfere with the signalling behind muscle contraction (Argireline, SNAP-8). And enzyme-inhibiting peptides, which block the matrix metalloproteinases that break collagen down.
Palmitoyl pentapeptide-4 has a 12-week double-blind, placebo-controlled, split-face trial in 93 women showing measurable reductions in wrinkles and fine lines. That is a real study design. It is also modest in effect, and considerably weaker than what retinoids achieve. A point most peptide marketing omits.
This is the single most useful thing to know about buying peptide skincare. Studies showing collagen changes with GHK-Cu used concentrations one to three orders of magnitude higher than typical over-the-counter serums, which contain roughly 0.001–0.01%. Most products fail not because the peptide is inactive but because it is present at a sub-effective dose. Concentration is rarely disclosed. Position on the ingredient list is the only crude proxy.
Melanotan I and II sit here nominally, but belong to a different risk class entirely. They stimulate melanocytes through MC1R, and carry documented adverse reports including changes in pigmented lesions and priapism. Advisory review is pending before February 2027. Nothing about the cosmetic evidence base extends to these.
Understanding a category is the first step. Whether any of it applies to you is a question for a licensed physician who knows your history.
See consultations