Lysine is an essential amino acid in human nutrition because the body cannot produce it. It must be obtained in food or by taking a supplement.

Lysine can be found in foods such as:

• yogurt
• fish
• cheese
• brewer's yeast
• wheat germ
• pork and other meats

Lysine which is one of the building blocks of protein may be used to help inhibit the growth of herpes viruses that cause cold sores and fever blisters.