Cold sores are caused by certain strains of the herpes simplex virus (HSV). HSV-1 usually causes cold sores. HSV-2 is usually responsible for genital herpes. However, either type can cause sores in the facial area or on the genitals.

You get the first episode of herpes infection from another person who has an active lesion. Shared eating utensils, razors and towels, as well as kissing, may spread HSV-1. Oral sex can spread HSV-1 to the genitals and HSV-2 to the lips.

While cold sores are most contagious when they are oozing fluid, the virus can be transmitted to others even during times when you have no blisters.

Once you've had an episode of herpes infection, the virus lies dormant in nerve cells in your skin and may emerge again as an active infection at or near the original site. Recurrence may be triggered by:

  • Fever
  • Menstruation
  • Stress
  • Fatigue
  • Exposure to the sun
May. 23, 2012

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