Oral herpes is an infection of the lips, mouth, or gums due to the herpes simplex virus. It causes small, painful blisters commonly called cold sores or fever blisters.

Oral herpes is also called herpes labialis (Herpes occurs on lips). Oral herpes is a common infection of the mouth area.

It is caused by the herpes simplex virus type 1 (HSV-1). Most people in the United States are infected with this virus by age 20.