Peptides in skincare, decoded

What peptides are

Short chains of amino acids - typically two to ten residues - designed to mimic fragments of larger signalling proteins. The logic is that a fragment can trigger a response the whole protein would trigger, while being small enough to formulate and, in principle, to penetrate. They are grouped by function: signal peptides that prompt matrix synthesis, carrier peptides that deliver trace metals, neurotransmitter-inhibiting peptides, and enzyme-inhibiting peptides.

The ones in this range

Copper tripeptide-1 (GHK-Cu) is a carrier peptide delivering copper, with the deepest literature of any cosmetic peptide, covering matrix remodelling and wound healing.

Palmitoyl pentapeptide-4 (Matrixyl) and palmitoyl tripeptide-5 are signal peptides; the palmitoyl tail is there to improve lipid solubility and therefore penetration. Palmitoyl tripeptide-5 is described as a TGF-beta mimetic.

Acetyl tetrapeptide-5 is associated with periorbital puffiness, acetyl tetrapeptide-2 with firmness, hexapeptide-9 with collagen IV and laminin, tripeptide-3 with neuromuscular signalling, dipeptide-2 with lymphatic drainage, nonapeptide-1 with pigment via MSH antagonism, and acetyl tetrapeptide-3 and biotinoyl tripeptide-1 with follicle and hair applications, where Vegalab uses them in the Scalp Repair line.

The concentration problem, said plainly

All nine peptides in the Youlief Peptiderma cream are present at exactly 0.00005% - 0.5 parts per million each. Palmitoyl pentapeptide-4 in the Setup Cream is at 0.05 ppm, ten times lower again.

Published peptide work generally uses concentrations orders of magnitude above this. At 0.5 ppm a peptide is present, and can be truthfully listed on a label, but it is not present at a level at which the mechanisms described above have been demonstrated to operate.

This matters more for peptides than for almost any other ingredient class, because peptide marketing leans heavily on mechanism - receptor names, signalling pathways, growth-factor comparisons - while the amount present is rarely mentioned. A reader who understands that a nine-peptide complex may contain 4.5 ppm of peptide in total is much better equipped than one who has only read the mechanism story.

None of this makes the products bad. It makes the peptide claim a minor part of what they do, and it means the ingredients doing the visible work are more likely the niacinamide, the squalane at 4%, the humectants and the barrier lipids.

What does Peptides in skincare, decoded not do?

They do not act like injectable neuromodulators, whatever the marketing implies. Penetration of larger peptides through intact stratum corneum is limited and remains a real formulation constraint. And peptide names are trade-driven rather than standardised, so two products naming different peptides may be doing much the same thing.