Lysine is an essential amino acid that is a necessary building-block for all protein. It aids in the production of antibodies, hormones, and enzymes. Lysine helps calcium absorption and maintains proper nitrogen balance. It helps in collagen formation, tissue repair, and helps build muscle. Lysine also has the capacity to fight off the herpes simplex virus, responsible for cold sores and genital herpes. It fights the virus by blocking arginine, and amino acid the virus needs to replicate itself. Lysine indeed performs important functions that help keep us in good health. 500 mg. 100 Tablets.