Cold sores, also known as herpes labialis, are caused by nongenital herpes simplex virus type 1. People can develop a cold sore on their lips or in their mouth.
Transmission of the nongenital herpes simplex virus type 1 (HSV-1) occurs during childhood through nonsexual contact, but adults can contract the infection through sexual activity. HSV-1 hibernates inside skin cells and neurons under the skin until a trigger stimulates it.
Stages of a cold sore
A cold sore develops in five stages and will typically last between 9 and 12 days.
Initially, people will feel a tingling, itching, or burning sensation underneath the skin around the mouth or base of the nose. Doctors call this the prodrome stage.
Other symptoms that may occur during this stage include: