Herpes Simplex Infections
(Cold Sores, Non-Genital)
Medical Authors: Mohamad El Mortada, MD, MaryAnn Tran, MD, Corrine Young, PharmD,
and Mary Nettleman, MD, MS
Medical Editor: Melissa Conrad Stöppler, MD
Introduction
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 when least expected (or desired). In between attacks, the virus hides deep in nerve roots. 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, once a month) 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 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 skin; or
- sometimes there is no apparent cause of the recurrence.
How is oral herpes 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 transmitting the virus. 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. 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.
Next: What are the signs and symptoms? »
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