Found while search Google:

Question in Yahoo Answers:

I just noticed a cold sore coming in and i have friends coming over and i need fast cure..?

The answer from another Yahoo user:
Trust me on this one, Sprits of Camphor, you can get it at your drug store. Apply it on the part that has the tingle. Then maybe three times a day apply it to your whole lip.
I have been hounded with cold sores for about 10 years, I always carry around the Camphor. I also use something called Repcillin. After applying the camphor for a few days I put on the Repcillin, the cold sores don't even show anymore. I use the two products as soon as I feel the itch!!!