Herpes simplex virus

Cold sores are caused by the herpes simplex virus (HSV). There are two types of herpes simplex virus: HSV-1 and HSV-2. Both virus types can cause sores around the mouth (herpes labialis) and on the genitals (genital herpes). A cold sore is usually caused by HSV-1. HSV-2 is the main cause of genital herpes. The herpes simplex virus usually enters the body through a break in the skin around or inside the mouth.

The virus is usually spread when a person touches a cold sore or touches infected fluid—such as from sharing eating utensils, sharing razors, kissing an infected person, or touching that person’s saliva. A parent who has a cold sore often spreads the infection to their child in this way. Cold sores can also be spread to other areas of the body/face.