Herpes labialis is an extremely common disease caused by infection of the mouth area with herpes simplex virus, most often type 1. Most Americans are infected with the type 1 virus by the age of 20.

The initial infection may cause no symptoms or mouth ulcers. The virus remains in the nerve tissue of the face. In some people, the virus reactivates and produces recurrent cold sores that are usually in the same area, but are not serious. Herpes virus type 2 usually causes genital herpes and infection of babies at birth but can also cause herpes labialis.

Herpes viruses are contagious. Contact can occur directly, or through contact with infected razors, towels, dishes, etc. Occasionally, oral/genital contact can spread oral herpes to the genitals (and vice versa), so people with active herpes lesions on or around their mouths or on their genitals should avoid oral sex.

The first symptoms usually appear within 1 or 2 weeks, and as late as 3 weeks, after contact with an infected person. The lesions of herpes labialis usually last for 7 to 10 days, then begin to resolve. The virus may become latent, residing in the nerve cells, with recurrence at or near the original site.

Recurrence is usually milder. It may be triggered by menstruation, sun exposure, illness with fever, stress, or other unknown causes.

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