Herpes labialis

Overview
Herpes labialis (also known as "Orolabial herpes" ) is an infection of the lip by herpes simplex virus. In many cases, it causes small blisters or sores on or around the mouth that are commonly known as cold sores or fever blisters. (In medical contexts, "labia" is a general term for "lip"; "herpes labialis" does not refer to the labia of the genitals, though the etymology is the same.) When the viral infection affects both face and mouth, the broader term "orofacial herpes" is used to describe the condition, whereas the term "herpetic stomatitis" is used to specifically describe infection of the mouth; "stomatitis" is derived from the Greek word stoma that means "mouth". Sores associated with herpes labialis typically heal within 2-3 weeks, but the virus that causes them is not removed from the body. The herpes virus infects and becomes dormant in the facial nerves, following orofacial infection, periodically reactivating (in symptomatic people) to create sores in the same area of the mouth or face that the original infection occurred.

Causes
Herpes labialis infection occurs when the herpes simplex virus comes into contact with oral mucosal tissue or abraded skin of the mouth. Infection by the type 1 strain of herpes simplex virus (HSV-1) is most common, though cases of oral infection by the type 2 strain are increasing.

Presentation
Herpes infections often show no symptoms; when symptoms do appear they typically resolve within two weeks. The main symptom of oral infection is inflammation of the mucosa of the cheek and gums -- known as acute herpetic gingivostomatitis -- which occurs within 5–10 days of infection. Other symptoms may also develop, including painful ulcers—sometimes confused with canker sores—fever, and sore throat. Primary HSV infection in adolescents frequently manifests as severe pharyngitis with lesions developing on the cheek and gums. Some individuals develop difficulty in swallowing (dysphagia) and swollen lymph nodes (lymphadenopathy). Primary HSV infections in adults often results in pharyngitis similar to that observed in glandular fever (infectious mononucleosis), but gingivostomatitis is less likely.

Recurrent oral infection is more common with HSV-1 infections than with HSV-2. Prodromal symptoms often precede a recurrence. Symptoms typically begin with tingling (itching) and reddening of the skin around the infected site. Eventually, fluid-filled blisters form on the lip (labial) tissue and the area between the lip and skin (vermilion border). The recurrent infection is thus often called herpes simplex labialis. Rare reinfections occur inside the mouth (intraoral HSV stomatitis) affecting the gums, alveolar ridge, hard palate, and the back of the tongue, possibly accompanied by  herpes labialis.

Treatment
Acyclovir has been used in some cases.