This post is going to be short and sweet. Topically applied collagen doesn't work. Period.
Since there is absolutely no ambiguity, I could leave it at that. However, some of you might crave a little background.
First a quick parenthesis on what collagen is. It is a protein that occurs in many places throughout the body. We are interested in it as the main supporting fiber within the dermis, giving strength, elasticity and structure. Its degradation (which you can help along the way by, for instance, smoking) causes wrinkles.
Topical application of collagen won't help reverse that process because collagen molecules are simply too large to penetrate the upper layer of the skin. Collagen pads are often sold to reduce puffiness and wrinkles around the eyes. They are a waste of money. Creams that use fish collagen (on the grounds that the molecular structure is the same as collagen in humans) don't work either.
Even if you lay off the fags, collagen will degenerate because there is an enzyme that actually chops it up and recycles it. High tech sounding skin care solutions claim they can inhibit these enzymes. Although it remains to be seen if they can work.
NB: collagen injections are a whole other ball of wax that I'll come back to in a future post.