My DH used to have cold-sores all the time when he was young! (Do the outbreaks lessen into adulthood???) Then, at the advice of a family-friend physician, he went on the Lysine, and it really helped. He does take it religiously.... don't remember the last cold-sore he's had now. Also, one thing that has not been menioned is Zovirax prescription ointment. Very expensive, but works! If they are really really bad, then I would consider a prescription like Zovirax or the others mentioned.
I sometimes get the ones inside the mouth. Canker sores. I found that when I switched to a toothpaste with baking soda and peroxide (Mentadent) I never got them! Temporarily used my former toothpaste... voila - broke out! Now I use a toothpaste with baking soda only (no peroxide) Arm and Hammer Brilliant Sparkle, and I still do not get the mouth sores! I just love to be able to pass this helpful info on to anyone plagued with this problem. I even swear that I caught the last bit of a toothpaste commercial yesterday that mentioned something like 'lessens canker sores'?????
Also, since Zinc is supposed to be antiviral - perhaps Zicam, used as a topical treatment. How about this alternated with treating with baking soda? Might be worth a shot.
And, what has been said is right... If the things get full-blown, then seems that NOTHING helps. Try to treat at the first little Tingle!
Good Luck, I know how excruciating these things can be!
PS: Are they for sure cold-sores if they are appearing on areas of dry skin and not mainly the mouth-nose??? Is it possible that it could be something different? May want to mention this to the Dr.