L-Lysine
I have seen posts recommending L-arginine supplements. Anyone taking arginine should know it competes with L-lysine for absorption.
L-lysine is needed to create collagen, so taking too much L-arginine could cause an L-lysine deficiency, which could limit the production of collagen.
What I am saying is: If you take L-arginine supplements, you should consider taking L-lysine if you want to grow more collagen. L-proline is also needed to produce collagen, but I don’t think it is affected by arginine, but it wouldn’t hurt to take proline with the lysine supplement.