A cold sore or fever blister—also called oral herpes—is an infection on or around the lips or mouth area caused by the herpes simplex virus type 1 (HSV-1). The virus is common. In fact, 8 out of 10 people have it. Most people get it by the time they’re 20 years old.
The virus lives in your nerve tissue. While “asleep,” the virus produces no symptoms. When it “wakes up,” the virus can affect your skin’s surface and cause a cold sore.
There is no cure for cold sores, but there are ways to manage your cold sore symptoms.