What Are Peptides?
Peptides are short chains of amino acids — typically 2 to 50 amino acids in length — that serve as signalling molecules in the skin, instructing cells to perform specific biological functions. In skincare, peptides are used to communicate with fibroblasts (signalling collagen production), modulate pigmentation, inhibit neuromuscular signals (the "Botox-like" peptides), and support barrier repair. Collagen itself is a protein, and as it degrades, the resulting peptide fragments act as feedback signals — prompting fibroblasts to synthesise more collagen. Synthetic peptides can mimic these signals.
Categories of Skincare Peptides
Signal peptides (e.g., Matrixyl/palmitoyl pentapeptide-4, copper peptides) signal fibroblasts to increase collagen, elastin, and hyaluronic acid synthesis. Carrier peptides (e.g., copper peptides GHK-Cu) deliver trace minerals needed for enzymatic skin repair. Neurotransmitter-inhibiting peptides (e.g., Argireline/acetyl hexapeptide-3) modulate muscle contraction signals to reduce expression lines. Enzyme-inhibiting peptides slow the enzymes that break down collagen.
Evidence Assessment
Peptide research is genuinely promising but the evidence base is thinner than for retinoids or antioxidants. Many peptide studies are small, short-term, industry-funded, and use ex-vivo models rather than in-vivo human clinical trials. The larger, more independent peptide literature (particularly for Matrixyl and GHK-Cu) is more compelling. Peptides work best as a complement to an established routine containing retinoids and antioxidants — not as standalone anti-ageing solutions.
Stability note: Many peptides are unstable and degrade rapidly. Formulation matters: look for peptides in airless pump packaging, formulated at a stable pH, and away from strong acids that can hydrolyse them.
See Barrier Repair and Collagen.