Collagen creams only work on the surface of the skin (Collagen is a huge molecule that sits on the surface of the skin and cannot be absorbed into the dermis. (Deanne Mraz Robinson. M.D)
Like many moisturisers mainly slow the rate of water loss from the skin and help keep the skin supple.
No moisturiser can undo the effect of collagen loss and make wrinkles disappear. We all know collagen decreases with age which causes dehydration, hence the lack of firmness and a dull complexion.
Fragments of collagen (fragments of proteins) polypeptides can be directly absorbed through the top layer of skin and deep into the cellular level to stimulate collagen growth. By stimulating collagen production, peptides help re-build collagen and boosts and locks in hydration giving your skin the impression of being plumper. Peptides amp up the skin cells and may help strengthen the skin barrier.
Focus on moisturisers that contain peptides that stimulate your collagen growth.