What Are Cold Sores?

Despite the name, when you get painful blisters called cold sores, don't blame your cold. Cold sores are caused by a virus, but not the kind that makes you sniffle and sneeze. Instead, they happen because of an infection with the herpes simplex virus (HSV).

Symptoms

Cold sores, also called fever blisters, can show up anywhere on your body. They're most likely to appear on the outside of your mouth and lips, but you can also find them on your nose, cheeks, or fingers.

After the blisters form, you may notice that they break and ooze. A yellow crust or a scab builds up and eventually falls off, revealing new skin underneath.

The sores usually last 7 to 10 days and can spread to other people until they crust over completely.

Who Gets Cold Sores?

Just about everyone. Ninety percent of all people get at least one cold sore in their life.

The symptoms are usually the most severe the first you time you get cold sores. Sometimes kids who are affected may become seriously ill.

After the first time you get cold sores, your body may develop antibodies, and you'll never have another infection. About 40% of U.S. adults, though, get repeated cold sores.

Cold sores generally are not serious, but the infection may be life-threatening for anyone who has AIDS or whose immune system -- the body's defense against germs -- has been curbed by other disorders or medications.

If you have a severe case of a skin condition called eczema, you may get cold sores over large parts of your body.

There can sometimes be serious complications from a cold sore. If the infection spreads to the eye, it could affect your vision. If it spreads to the brain, it could lead to meningitis or encephalitis.

What Causes Cold Sores?

Herpes Simplex

There are two types of herpes simplex virus that can cause cold sores: HSV type 1 and HSV type 2. Cold sores are usually caused by HSV type 1.

You usually catch HSV when you come into contact with people or things that carry the virus. For instance, you can get it from kissing someone who's infected or when you share eating utensils, towels, or razors.

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Both HSV type 1 and type 2 can cause sores on your genitals. They can be spread by oral sex. Genital herpes is usually caused by HSV type 2.

You may get cold sores as late as 20 days after you came into contact with the virus. Once the virus enters your body, the cold sore may appear near the part it entered. About 2 days before an attack, you may get itchy or feel sensitive at the spot.

Some things can trigger an outbreak, such as:

To protect other people, when you have cold sores, don't:

  • Kiss anyone
  • Share forks, knives, spoons, glasses, towels, lip balm, or razors
  • Have oral sex
WebMD Medical Reference Reviewed by Neha Pathak, MD on September 21, 2017

Sources

SOURCES: 

Columbia University College of Dental Medicine: "Cold Sores and Fever Blisters."

Mayo Clinic: "Cold Sore."

Academy of General Dentistry: "What Are Cold Sores?"

MedlinePlus: "Herpes - oral."

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