Cold sores are small, painful, fluid-filled blisters. They are usually found at the border of the lip.

Herpes Simplex on the Lips
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Cold sores are caused by 2 types of herpes simplex viruses. Cold sores are common. In most cases, people contract the virus as young children.

You may get the virus from:

  • Contact with the fluid from a cold sore of another person, or genital herpes sores
  • Contact with the eating utensils, razors, towels, or other personal items of a person with active cold sores
  • Sharing food or drink with a person with active cold sores
  • Contact with the saliva of a person who has the herpes virus even if no sores are present

The first episode of illness with herpes virus can cause a body-wide illness. After that, the virus lies quietly in the skin until it is reactivated. The reactivated virus causes a cold sore to appear.