I started getting cold sores when I was a little kid. It was awful. Probably the virus was transmitted in utero, because my mother is the only other one in the family who gets them.
When I was in my twenties, my doctor recommended lysine, which if you take it every day, will help most people to avoid outbreaks. It's a cheap supplement and good for you anyway. Avoid arginine, either supplements or foods rich in arginine.
Dynamiclear is a product that kicked my cold sores into the next universe. It was marketed for all herpes virus outbreaks. When I applied it, it felt like someone had punched me in the mouth. Really painful for a minute, but the cold sore healed much more rapidly than usual and I didn't have another outbreak for years. Even now if I do get an outbreak, it's really mild. It's sold on Amazon and I don't know if it's the same formula or not, but if it is, I recommend trying it.