People take Lysine for skin and lip health, mainly to aid in collagen production and reduce the reoccurrence of cold sore breakouts.** Lysine is an essential amino acid that is a necessary building block for all protein**. Like its fellow amino acids, the main task of lysine is to help build protein** – although that’s far from all it does. Lysine is also an important player in the production of various enzymes, hormones, and immune compounds. Lysine is also used for the health and integrity of skin and lips, and plays an important role in immune system function**.