Cold Sores (Nongenital Herpes Simplex Infections)

  • Medical Author:

    Sandra Gonzalez Gompf, MD, FACP is a U.S. board-certified Infectious Disease subspecialist. Dr. Gompf received a Bachelor of Science from the University of Miami, and a Medical Degree from the University of South Florida. Dr. Gompf completed residency training in Internal Medicine at the University of South Florida followed by subspecialty fellowship training there in Infectious Diseases under the directorship of Dr. John T. Sinnott, IV.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Cold Sores Slideshow

What makes herpes (cold sores) recur?

After infection, the virus enters the nerve cells and travels up the nerve until it comes to a place called a ganglion. There, it resides quietly in a stage that is referred to as "dormant" or "latent." At times, the virus can become active and start replicating again and travel down the nerve to the skin, causing sores and blisters. The exact mechanism behind this is not clear, but it is known that some conditions seem to trigger recurrences, including

  • a fever, a cold, or the flu;
  • UV rays (exposure to the sun or a sunburn);
  • emotional or physical stress (such as an illness or surgery);
  • weakening of the immune system;
  • trauma to the involved area such as dental work; and
  • sometimes there is no apparent cause of the recurrence.

Are cold sores contagious?

Oral herpes is contagious to others who do not have it.

How do cold sores spread?

The virus is spread from person to person by kissing, by close contact with herpes lesions, or from saliva even when sores are not present. Infected saliva is a common means of virus transmission. The contagious period is highest when people have active blisters or moist sores. Once the blisters have dried and crusted over (within a few days), the risk of contagion is significantly lessened. HSV can also be spread through personal items that are contaminated with the virus, such as lipstick, utensils, and razors. Despite popular myth, catching herpes (cold sores) from surfaces, towels, or washcloths is a very low risk, since the virus does not usually survive long on dry surfaces.

Medically Reviewed by a Doctor on 6/15/2016

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