re: Cold sore remedies...any way to stop one once it has already gotten going?

Some people say tea tree oil directly on the spot can help if it hasn't broken out. Can't confirm, if you have Abreva would probably work better. But I wouldn't advise tea tree oil once they break out... that seems to anger them. (I haven't had cold sores, but was lucky enough to get shingles (I believe the same virus) on my face last year when I tried the tea tree oil.)

If you don't stop it in time and it blisters, I do recommend bentonite clay... I tried that a day or two later than the tea tree oil and it practically dried them out overnight and they healed quickly from there. (Note: you're supposed to mix the clay in water with wood or plastic spoon, or your finger; should't use metal spoon as the clay is supposedly highly ionic and contact with metal draws electrons out & diminishes effectiveness.)