Oral herpes (herpes labialis) is most often caused by herpes simplex virus 1 (HSV-1) but can also be caused by herpes simplex virus 1 (HSV-2). It usually affects the lips and, in some primary attacks, the mucous membranes in the mouth. A herpes infection may occur on the cheeks or in the nose, but facial herpes is very uncommon.
Primary Oral Herpes Infection. If the primary (initial) oral infection causes symptoms, they can be very painful, particularly in small children.
- Blisters form on the lips but may also erupt on the tongue.
- The blisters eventually rupture as painful open sores, develop a yellowish membrane before healing, and disappear within 3 - 14 days.
- Increased salivation and foul breath may be present.
- Rarely, the infection may be accompanied by difficulty in swallowing, chills, muscle pain, or hearing loss.
In children, the infection usually occurs in the mouth. In adolescents, the primary infection is more apt to appear in the upper part of the throat and cause soreness.
Recurrent Oral Herpes Infection. Most patients have only a couple of outbreaks a year, although a small percentage of patients experience more frequent recurrences. HSV-2 oral infections tend to recur less frequently than HSV-1. Recurrences are usually much milder than primary infections and are known commonly as cold sores or fever blisters (because they may arise during a bout of cold or flu). They usually show up on the outer edge of the lips and rarely affect the gums or throat. (Cold sores are commonly mistaken for the crater-like mouth lesions known as canker sores, which are not associated with herpes simplex virus.)