Simply put, Lysine is an amino acid that your body can't produce on it's own. You have to get your Lysine intake from what you eat or dietary supplements. High levels of Lysine can be found in cheese, yogurt, eggs, beef and pork.
Lysine works by stopping the herpes virus from replicating itself and therefore becoming weaker. There has been lots of research over the years confirming that a regular intake of Lysine will reduce the number and severity of outbreaks.
So how much to take? Studies have suggested that between 1000mg and 1500mg per day is a good dosage to take to help fight cold sores and herpes. I myself take 2000mg a day (2 x 1000mg tablets) per day, and I can honestly say that along with a combination of other things, that I wouldn't do without it.
Kal's L-Lysine 1000mg 100Tabs
Keeping a supply of Lysine and taking it regularly will definitely help with keeping the virus at bay.