Why would collagen & elastin added to skin creams be unlikely to penetrate the skin as some ads. imply they do

there is a basal layer under the skin producing cells which is very hard to penetrate by macromolecules as collagen and elastin - these can be used in the layers above and show effect - but not a lasting one as these cells are constantly replaced|||The molecules are way too big to penetrate skin. And even if they did they will not do anything. Collagen and elastin are parts of the dermis. Adding them afterward in skin will simply do nothing.|||probably because collagen molecule is too big to go through cellular boundaries