Basics
What are peptides?
Short chains of amino acids—the same building blocks as proteins, just smaller. Here is how that shows up on your label.
The simple version
Peptides are tiny protein fragments. Think of a full protein as a long necklace of beads; a peptide is a short stretch of that necklace—often 2 to 50 amino acids. In skin care, hair care, supplements, and medicine, brands use them as signal molecules: little messages that nudge cells toward repair, collagen talk, lash growth, or other effects.
Why labels look scary
Cosmetic regulations require INCI names—standardized ingredient names. So you see Palmitoyl Pentapeptide-4 instead of Matrixyl, or Acetyl Hexapeptide-8 instead of Argireline. Same molecule, two naming systems: marketing nicknames up front, INCI on the back.
Not one thing
“Peptide” is a category, not a single ingredient. Copper tripeptide, collagen hydrolysates, GLP-1 drugs, and lash serums all contain peptides—but they work differently, have different evidence, and belong in different conversations.