Herpes

Herpes: A family of viruses. Herpes also refers to infection with one of the human herpesviruses, especially herpes simplex types 1 and 2.

Herpes simplex type 1, also known as human herpesvirus 1 (HHV-1), causes cold sores and fever blisters in the mouth and around it. Here is a depiction of a typical fever blister on the lip caused by HHV-1: