Herpes (cold sores) is possible, but I'm not sure from your description, and it would be unlikely, if not impossible, for it to come back this quick. My advice is to see your doctor right away, because a look and perhaps a culture at this stage will tell you with greater certainty what it is. If it isn't a cold sore, it probably isn't anything serious either--just an irritation of some sort, and more than likely nothing contagious. But why speculate--get a precise diagnosis and then you'll know where you're at and what to do.
Best.
Dr. Rockoff
ever since i stopped using it, my lips have been fine..it's been over a month now and that irritation never came back after that 2nd time... so i guess it wasn't a coincidence the night i used it again and it came back.
now i use vaseline instead and they've been happy.