Lysine is an essential amino acid, meaning it is not naturally produced by the human body and must be obtained from our diets. It is a building block for proteins and has a range of important roles in the body, including assisting with the absorption of calcium and helping to produce antibodies and collagen. It is also involved in the formation of hormones and enzymes, and has been linked to the prevention of hair loss, and even the improvement of the appearance of skin and nails. Additionally, Lysine has been used to help treat cold sores, improve recovery from athletic injuries, and even manage anxiety and stress.