Uch, cold sores are the bane of my existence. When I was in high school, I never had bad skin, but I felt like cold sores were my trade-off for not having acne, and I always used to say that I'd rather have a jillion zits every day than one cold sore a year! I used to get them like every three months when I was a teen, then I got one while sick and pg with DS1 in December '04, then that was it for four and a half years! Then this past May, like literally a day or two after remarking to an old friend who revealed to me that she had genital herpes (um, yikes) that I had face herpes but hadn't had a cold sore in nearly five years, of course I got one! I'd been sick like four times in a row right before that, though, so that's probably why I got one - reduced immune function brings them out on me.
So is it an internal pH thing only, or is it also a girl hormone thing too? Because I've heard some people get them near AF, so maybe it's the hormones, too. Mostly mine have come out when I've been sick for a long time, or I don't use Carmex and my lips get really chapped, or when I diet too much and get too thin (but that goes hand in hand with the sick all the time).
Great, so if I ever do finally get pg with a girl, that's what I have to look forward to 
? Oh well, it would be worth it!