Collagen: topical versus oral

The size problem

Native collagen is a triple-helical protein of roughly 300,000 daltons. Nothing that size crosses intact stratum corneum. Hydrolysed collagen is broken into peptides of a few hundred to a few thousand daltons, which improves the situation without solving it. The idea that applied collagen is incorporated into the dermal collagen network has no support and should not be implied.

What topical collagen actually does

Two things, both real and both modest. Hydrolysed collagen and collagen peptides are effective humectants and film formers — they hold water at the surface and improve immediate smoothness and feel. And there is some evidence that specific collagen-derived peptides act as signalling fragments, prompting fibroblast activity, which is the more interesting claim and the one that overlaps with the peptide literature.

The nine forms here

The Youlief range lists hydrolyzed collagen, collagen extract, collagen, collagen amino acids, soluble collagen, atelocollagen, soluble collagen crosspolymer, potassium myristoyl hydrolyzed collagen and rosin hydrolyzed collagen. Vegalab uses hydrolyzed collagen and recombinant elastin in the Bio-Thread cream.

Levels run from 6 ppm for hydrolyzed collagen down to 0.1 ppm for atelocollagen. As with the HA family, a long list of collagen variants indicates formulation intent rather than substantial collagen content. Atelocollagen — collagen with the immunogenic telopeptides removed — is a genuinely interesting material in medical contexts, but not at 0.1 ppm in a cream.

Oral collagen, since readers will ask

This is a separate question with a real and improving literature. Several trials report improvements in skin hydration and elasticity with hydrolysed collagen peptide supplementation, with proposed mechanisms involving specific dipeptides surviving digestion and reaching skin. The evidence is better than sceptics allow and weaker than supplement marketing claims, and much of it is industry-funded. It deserves its own page rather than a paragraph.