Glossary
Cosmetic Peptide (Signal Peptide)
Skin-care peptides are sorted into signal, carrier, enzyme-inhibiting and neurotransmitter-modulating types. Reading INCI labels and weighing the data.
In skin-care science, short synthetic sequences made for topical use are traditionally sorted into four functional families. The largest family is the signal peptides: fragments that imitate products of matrix breakdown and, in fibroblast culture, are reported to boost collagen and extracellular matrix production; the standard cases are Palmitoyl Tripeptide-1 and Matrixyl (palmitoyl pentapeptide-4), and the class overlaps with the matrikine idea. The neurotransmitter-modulating family — Argireline, SNAP-8 — consists of SNAP-25 fragments 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. An INCI label like "palmitoyl pentapeptide-4" only follows a nomenclature convention and says nothing about efficacy.
Related terms and material
Compare the tetrapeptide, tripeptide and in vitro entries. In the catalogue: signal peptides for cosmetic research, plus Matrixyl and Argireline; background in our guide to topical peptides.