Imagine this: You and your mother are having a heated discussion about whether the sudden appearance of a sore on your lip is a fever blister or a cold sore. You know you can win this battle, and you respond with an I’ll-show-you retort: "Let's ask Mr. Google," you say. Both of you whip out your smart phones, and ...a family crisis is averted. It turns out you’re both right, according to John Hopkins Medicine. Case in point, this annoying sore is known by both names, and is caused by the virus "herpes simplex," or oral herpes (HSV-1).