Collagen

Collagen is a large structural protein that gives the dermis much of its tensile strength. In topical cosmetics, native collagen is too large to simply replace lost dermal collagen, so its main direct role is film-forming and moisturizing at the skin surface.

Hydrolyzed collagen is broken into smaller peptides and is easier to formulate, but these fragments still do not rebuild the skin's collagen network by being laid into it like spare parts. Topical collagen products are best understood as conditioning and hydrating formulas, with any additional effects depending on peptide size and formulation.