Docosanol
"I have suffered from cold sores my entire life. Abreva is the only thing that works for me. It is a miracle drug! I also start taking L-lysine at the first sign of a cold sore. the two things in combination have turned me lifelong suffering into a barely noticeable minor irritation. The only complaint I have is the new pump bottle which dispenses more cream than needed. The medicine is too expensive to waste like that."