Purica L-Lysine Powder - One of the 8 essential amino acids necessary for normal growth, development and maintenance of health. L-Lysine plays a part in collagen formation and calcium absorption as well as carnitine production to convert fatty acids into energy. Lysine is also commonly used to help prevent and treat viral infections such as cold sores and shingles. In addition, L-Lysine may help to support a healthy immune system and proper cardiovascular function.