Herpes simplex type two causes fever blisters on the lips as well. And a herpes simplex type two outbreak is often accompanied by a fever. But this type of herpes also causes genital blisters.
The best way to avoid cold sores or fever blisters it to take supplements like lysine when one feels the blister coming on. Before a blister pops up, there is usually itching and discomfort on my lip. As soon as I start feeling this, I take lysine capsules that I get from the pharmacy. The blister usually doesn't develop if I start taking lysine early.