Cosmetic Peptide (Signal Peptide)

Cosmetic peptides are short synthetic sequences designed for application to the skin. By convention they are grouped into four functional classes. Signal peptides form the biggest class: fragments that imitate products of matrix breakdown and, in fibroblast culture, are reported to boost collagen and extracellular matrix production; Matrixyl (palmitoyl pentapeptide-4) and Palmitoyl Tripeptide-1 are the textbook examples, and the class overlaps with the matrikine idea. Neurotransmitter-inhibiting peptides such as Argireline and SNAP-8 are fragments of SNAP-25 investigated as competitive disruptors of SNARE complex formation. Carrier peptides transport trace metals, mainly GHK-Cu. Enzyme-inhibitor peptides act on MMPs or tyrosinase.

Judging the evidence

Two reservations apply across the category. To begin with, most published data come from fibroblast or explant models; controlled split-face studies in humans are rarer and are usually run by the manufacturer. Beyond that, skin penetration is the bottleneck — hydrophilic peptides pass poorly through an intact stratum corneum, which is why palmitoylation turns up so frequently in INCI names. A designation such as "palmitoyl pentapeptide-4" is simply a naming rule and says nothing about efficacy.

Related terms and material

tripeptide · tetrapeptide · in vitro. Reference material: cosmetic signal peptides, Matrixyl, Argireline. Further reading: topical peptides guide.