More than likely because u were feeling unwell, the cold sores came cause of that, if you get run down and are prone to cold sores u can bet they will appear then, when i get coldsores i feel fluey until they go away, i just had a bout of them, and felt like rubbih, they are horrible things but vaseline will do no good at all for them, u need something we call in the uk zovirax, this also is no good if u apply it too late, u need to pummel ur lips with it as soon as u feel tingling. once u start to feel better the cold sores will disappear, but like me always have a zovirax in ur purse u never know when one will strike good luck :confused: