A viral infection usually causes cold sores (fever blisters), which are contagious. Cold sores are tiny, painful, fluid-filled blisters.

Type 1 of the herpes simplex virus (HSV-1) causes cold sores, also called oral herpes.

Type 2 of the herpes simplex virus (HSV-2) affects the genital region. HSV-1 can also spread from the mouth to the genitals.12

Cold sores often appear in clusters on or around the lips.

You may experience a tingling sensation in the affected area before a breakout.

Treatment Options

There’s no cure for cold sores, and they often go away after a few weeks without treatment. Antiviral medications can speed recovery.14 A healthcare provider may also advise antiviral medications to prevent cold sores if you have frequent outbreaks.