Docosanol
"I get a cold sore every one to two years. I've tried home remedies and haven't had much luck. It was my first time using Abreva yesterday. Felt the cold sore coming on in the morning around 5am. I made a trip to the store after a 9 hour work day. Thought I would give it a try as it was the most expensive. I applied it immediately when I got into the car and every 2 hours after that. By 10pm it had already blistered and started to decrease in size. I've applied it three more times today and by 1pm you could barely notice it. Abreva knocked out my cold sore like boss!"