Cold sore fact sheet--a basic review.

What are cold sores?

Cold sores, also known as herpes labialis or fever blisters, are highly contagious open sores on the lip and outer edge of the mouth. When cold sores occur, the skin is often red and inflamed, and the blisters may break open, secrete a clear fluid, then crust over before healing.

Cold sores are generally caused by the herpes simplex virus 1, or HSV-1. This virus is part of the same family of viruses that causes chickenpox (varicella), shingles (herpes zoster), genital herpes (herpes simplex virus 2 or HSV-2), and mononucleosis. Since cold sores are caused by a virus and are considered a medical condition, your doctor can actually help. A prescription can be written for an antiviral medicine, one that targets the herpes virus.

How common are cold sores?

While the majority of the population has been exposed to HSV-1, not everyone develops cold sores. It has not been determined why certain people develop cold sores and others do not, but it is estimated that up to 24% of the adult population in the United States has had a cold sore at some point. (1)

What is the difference between HSV-1 and HSV-2?

Herpes simplex virus 1 (HSV-1) most commonly causes herpes labialis (cold sores) with an increasing number of genital HSV-1 cases being reported; these are suspected to be caused through oral sex. Herpes simplex virus 2 (HSV-2) is a contagious virus primarily causing outbreaks of genital herpes.

How are cold sores contracted?

Most people get the herpes virus for the first time as infants or young children. The virus usually enters a person's body through a break in the skin inside or around the mouth. HSV-1 lives inside your body in the nerves. Following some trigger event, the virus "wakes up" or is reactivated and travels through the nerve endings toward your lips. You may feel a tingling, itching or burning sensation beneath the surface of the skin, usually around the mouth or base of the nose. These symptoms are the beginning of a cold sore, or prodrome stage. Within a day or so, small red bumps appear in a group, which then begin to blister into a full-blown cold sore. After a few days, the blisters dry up and form a yellow crust. The crust eventually falls off leaving a red tender area. The redness fades as your immune system sends the herpes virus back into hiding. Once the cold sore has run its course, the virus goes back to "sleep," waiting for something to trigger it into action again. The virus will likely become active again causing cold sores, as most people affected have two to three cold sores a year. (1)

What are the symptoms associated with cold sores?

The first episode of HSV-1 infection often does not cause symptoms. If it does cause cold sore symptoms, they are usually more severe than those that may develop during recent outbreaks. Symptoms of a primary attack may include:

* Mouth soreness that makes it uncomfortable to eat, drink and sleep

* Fever * Sore throat * Swollen glands in the neck

Are cold sores contagious?

Cold sores, like other herpes viruses, are highly contagious and can be spread through physical contact. During outbreaks, people should avoid physical contact with others, like kissing and oral sex, and not touch the blisters. What can trigger a cold sore? Experts still do not know exactly how the herpes virus is reactivated. But they do know certain things can reactivate or "trigger" cold sores. Some of these triggers include:

* Exposure to sunlight (especially on the lips) * Stress * Fatigue, being "run-down" * Dental treatment * Mouth trauma, such as an injury to the lips or gums cut from shaving. * Other infections, such as a cold or flu * Food allergies * Menstrual cycle * Pregnancy

How are cold sores diagnosed?

Doctors can usually diagnose cold sores by conducting a simple examination, as the appearance of cold sores is often so typical that no further testing is required.

However, if it is not clear the problem is cold sores, a sample of fluid from the sore may be taken and sent to a laboratory for analysis. A blood sample can also be drawn and sent to the lab to be run through an HSV-1 type specific blood test.

What precautions can be taken?

If blisters are present, there are certain precautions that can be taken to reduce the likelihood of spreading the virus:

* Avoid physical contact with others, like kissing and oral sex * Wash hands frequently * Minimize the touching of eyes, nose, mouth or genitals, and women should be especially careful when applying or removing makeup

How are cold sores treated?

There are three options for dealing with cold sores:

1. Since cold sores are caused by a virus and are considered a medical condition, your doctor actually can help. A prescription can be written for an antiviral medicine, one that targets the herpes virus. These medications may relieve symptoms and may shorten the time to healing of cold sores.

2. Over-the-counter products may provide some symptomatic relief but most have not been shown to shorten the time to healing of cold sores.

3. If not treated, cold sores will eventually heal on their own after 7-10 days.

(1) Crumpacker CS, Guelic RM (1999). Herpes simplex. In IM Freedberg et al., eds., Fitzpatrick's Dermatology in General Medicine. 5th ed., vol. 2, pp. 2414-26. New York: McGraw-Hill, Inc.