I get a cold sore on my lip once or twice a year, usually brought on by stress, lack of sleep, being sick or out in the sun or any variation of the above. Once or twice a year....not bad right? But my lip swells sooooo much and they're so painful for me. My mom gets them the same way, as did my Grandmom. Can you be prone to them hereditarily? Is there an everyday medication to prevent them? I've been perscribed Famvir before, but that's only a couple day type thing.