This a contagious viral infection caused by a virus known as herpes simplex. There are two major types of herpes simplex virus known as type 1 and type 2. The type 1 herpes simplex is the major cause of oral herpes known as cold sores. It usually develops on oral tissues of your body such as mouth, lips and other parts of the face.
Herpes simplex virus type 2 usually causes genital herpes although it can also affect other oral tissues but in rare cases. A big percentage of the oral tissue infections such as the blister on lip or cold sores are caused by type 1.
Once you get infected with herpes simplex virus, the virus remains in your body permanently after the outbreak. It travels and hide deeper into the nerves of your cheekbone in a dormant state. It can either remain inactive permanently or it can occasionally travel down in the nerves to the skin surface to cause a recurrence of the infection.