Cold sore

A cold sore is a small, fluid-filled blister, usually on or around the lips, caused by herpes simplex virus infection. It can recur when the virus reactivates from latency in sensory nerves.

Herpes simplex virus: A group of viruses that establish lifelong infections and can cause oral or genital sores. Cold sores are most often caused by herpes simplex virus type 1.
Oral herpes: Herpes simplex virus infection affecting the mouth, lips, or nearby skin. Cold sores are a visible manifestation of oral herpes.
Aphthous stomatitis: A condition causing painful, shallow ulcers inside the mouth, commonly called canker sores. Unlike cold sores, aphthous ulcers are not caused by herpes simplex virus.
Recurrent herpes labialis: Repeated outbreaks of herpes simplex virus lesions on the lips or nearby skin. Cold sores commonly recur when latent virus reactivates.
Herpes simplex virus type 1: A herpesvirus that commonly causes oral infection and can also cause genital herpes. It causes most cold sores and remains latent between outbreaks.
Herpes simplex virus test: A laboratory test that detects herpes simplex virus or the immune response to it. A swab of a fresh lesion can help confirm the cause when diagnosis is uncertain.
Angular cheilitis: Inflammation and cracking at one or both corners of the mouth. Its corner-of-mouth fissures can be mistaken for cold sores but have different causes.
Asymptomatic shedding: Release of infectious virus from a person who has no visible symptoms. Herpes simplex virus can spread even when no cold sore is present.
Viral latency: A state in which a virus persists in host cells with limited or no active replication. After oral infection, the virus persists in sensory nerve cells between outbreaks.
Acyclovir: An antiviral medicine that inhibits replication of herpes simplex virus and related viruses. Early use can shorten some cold-sore outbreaks.

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HerpesBroader topic: It is the familiar visible form of oral herpes.