Lysine is an amino acid (building block of protein). People use it to make medicine. Lysine is used for preventing and treating cold sores. It is taken by mouth or applied directly to the skin for this use. Lysine is a building block for protein. It's an essential amino acid because your body cannot make it, so you need to obtain it from food. L-lysine is the form of lysine your body can utilize. It's naturally found in food and is the type used in supplements.

May Protect Against and Treat Cold Sores by Blocking Arginine.

May Reduce Anxiety by Blocking Stress Response Receptors. 

May Improve Calcium Absorption and Retention. 

Can Promote Wound Healing by Helping Create Collagen. 

Top Food Sources and Supplements.