.Scientific data on some lysine benefits are not yet conclusive. However, many people are exploring the use of lysine supplements, particularly in athletes and people who do not eat animal products. It is best to discuss the use of any supplement with a doctor. Lysine is an amino acid (building block of protein). Unlike some other amino acids, the human body cannot make lysine; therefore it must be eaten in the diet. Sources of lysine include meat, fish, dairy, eggs, and some plants such as soy and other legumes.Lysine is taken by mouth or applied directly to the skin for preventing and treating cold sores (caused by the virus called herpes simplex labialis).Lysine is taken by mouth to improve athletic performance and for improving symptoms of schizophrenia. Lysine is also used to reduce symptoms of canker sores, and for diabetes, high triglyceride levels in the blood, muscle strength, stress, and a metabolic condition called metabolic alkalosis.