All collagen products are beneficial for your skin right? It’s understandable if you group all collagen products in the same category, but be careful here because they’re not all the same. To simplify this, there are two ways to see collagen products:
1. Ingesting Collagen. Your body can then use that collagen to go fix connective tissue of all kinds (its superpower!) In other words, effective.
2. Rubbing Collagen into your skin. Purely cosmetic. In other words, NOT effective.

The benefits of collagen in improving hair, skin & nails, are no doubt compelling. Ageing skin is down to collagen, or more accurately, a lack of it. Pretty much every desirable part of healthy skin comes down to collagen content: The more of this protein we have, the firmer, plumper, and better our skin looks.
But as we age—doing things like smoking, drinking, and get too much UV exposure while aging—our collagen production drops off, and the collagen we already have starts to break down. This causes wrinkles, as well as a loss of plumpness or fullness. Addressing these symptoms means somehow addressing collagen loss.
Can a moisturizer or supplement really help your skin cells produce more collagen in the same way as ingesting it orally can?
The structure of collagen is like a braid or rope: Individual amino acids link up to form long chains, which bundle together to form thicker strands. Those strands then twist and coil around each other to form triple helices. Finally, those helices connect end to end and stack on top of each other to form clusters called fibrils. In other words, collagen is a pretty complex and massive molecule.
That’s why creams formulated with pure collagen simply can’t live up to their lofty claims— those huge braided molecules are just too big to penetrate your epidermis, and definitely too big to get down into the dermis where the real magic happens. So even though collagen creams feel nice and may help moisturize the skin, that’s about it in terms of benefits.
Your skin might feel softer and smoother, your wrinkles might look less prominent, which can be effective on the surface, but that is it, it’s just on the surface.

References
1. https://cbsupplements.com/cc/do-collagen-creams-work/
2. https://www.self.com/story/collagen-creams-supplements-skin
3. https://clairehill.com.au/blogs/news/do-collagen-creams-work