What causes cold sores?

Herpes virus returns: Cold sores on the lips or near the lips, are usually caused by recurrent oral herpes virus. They start as a slightly raised reddish area, then form a cluster of tiny blisters, which break open soon, leaving a sore (ulcer) to heal up over a week. Sores appear more often when one is under stress or is ill from another illness. Younger babies with herpes should see a doctor when a sore appears.

Herpes virus: Cold sores are caused by the herpes simplex virus (hsv). There are two types of herpes simplex virus: hsv-1 and hsv-2. Both virus types can cause sores around the mouth (herpes labialis) and on the genitals (genital herpes).

Herpes simplex virus: Oral herpes, occurs with symptoms of cold sores or fever blisters, is an infection of the mouth and cause by herpes simplex virus type 1 and type 2. After initial infection, the viruses are transported to the sensory nerve cell bodies, where they become latent and reside lifelong. Upon trigger, these virus then multiplies new virus particles, transport, and releases to the nerve terminal.