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Cold Sores
(Herpes Simplex Infections, Non-Genital)

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Medical Author:

Mohamad El Mortada, MD

Medical Author:

MaryAnn Tran, MD

Medical Author:

Corrine Young, PharmD

Medical Author:

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

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Medical Editor:

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.

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What are herpes simplex infections?

Herpes simplex virus (HSV) can cause infections that affect the mouth, the face, the genitals, the skin, the buttocks, and the anal area. This article will concentrate on non-genital herpes. Many people acquire the virus and have no symptoms. For others, painful blisters appear near the area where the virus entered the body. Typically, the blisters heal completely but reappear at some point in the future when least expected (or desired). In between attacks, the virus resides deep in the roots of the nerves that supply the involved area. When herpes simplex lesions appear in their most common location, around the mouth and lips, people often refer to them as "cold sores" and "fever blisters."

What causes cold sores?

There are two types of HSV, type I and type II. In general, type I, also known as herpes labialis, causes infections above the waist, most commonly as oral "cold sores." Type II infections occur mainly below the waist, leading to genital herpes. However, both types of HSVs are capable of infecting the skin at any location on the body.

Herpes infections, no matter where they occur first, have a tendency to recur in more or less the same place. Such recurrences may happen often (for example, several times per year) or only occasionally (for example, once or twice a year).

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 lays 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 be associated with recurrences, including

• a fever, a cold, or the flu;



• ultraviolet radiation (exposure to the sun);



• stress;



• changes in the immune system;



• trauma to the involved area;



• sometimes there is no apparent cause of the recurrence.

How do cold sores spread?

Infections caused by HSV are contagious. The virus is spread from person to person by kissing, by close contact with herpetic lesions, or even from contact with apparently normal skin that is shedding the virus. Infected saliva is a common means of virus transmission. People are most contagious when they have active blister-like sores. Once the blisters have dried and crusted over (within a few days), the risk of contagion is significantly lessened. However, a person infected with HSV can pass it on to another person regardless of the presence or absence of symptoms and visible sores or blisters. This is because the virus is sometimes shed in saliva even when sores are not present. Despite popular myth, it is almost impossible to catch herpes (cold sores) from surfaces, towels, or washcloths.

Picture of cold sores on the lips (fever blisters, HSV-1, or herpes simplex infection type 1)