Cold sores—those annoying little blisters that pop up around the lips—are far more common than most people realize. Also known as fever blisters, they’re caused by the herpes simplex virus type 1 (HSV-1), one of the most widespread viruses in the world.
According to the World Health Organization (WHO), about 67% of people under age 50 are infected with HSV-1. Many never develop visible symptoms, while others deal with recurring outbreaks that can be painful, embarrassing, and frustrating.