Abreva
"this and campho phenique are the best cold sore medicines you can get, or at least for me they work. The catch is I have to apply them immediately  after I feel the uncomfortable tingling, even before it breaks through the skin. If I wait for even a small bump to form before applying it, it will take at least 5-6 days before it starts to disappear. But if I do it immediately, the cold sore won't form. I'm on day 3 and my cold sore is almost gone. It bumped up very slightly the 2nd day but it wasn't even noticeable. It didn't turn red or white or that gross yellow color when it scabs over. Just looked like an incredibly tiny skin toned pimple.  And now it's smaller and flat and almost completely gone. But tonight it will be none existent "