herpes simplex
"I've gotten cold sores since I was young. It's a common thing among a lot of people, but it happens to me normally once a year around winter. My lips end up drying out and when they get chapped that's when a cold sore ends up forming. I  am not completely sure why, but whatever makes it lay dormant gets aggravated. I actually went to a local drug store to get a cold sore treatment when I found Lysine. Unfortunately, I didn't catch it in time but it took the pain and itching away almost immediately. It's shortened the amount of time it would normally take a cold sore to heal when the blisters have already formed. It's better than the other products I have used, and a lot more efficient."