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Diseases and Conditions
Cold sore
From MayoClinic.com
Special to CNN.com


The scenario is all too familiar: You feel a tingling on your lip and a small, hard spot that you can't yet see. Sure enough, in a day or two, red blisters appear on your lip. It's another cold sore, probably happening at a bad time, and there's no way to hide it or make it go away quickly.

Cold sores — also called fever blisters — are quite different from canker sores, a condition people sometimes associate them with. Cold sores are caused by the herpes simplex virus, and they're contagious. Canker sores, which aren't contagious, are ulcers that occur in the soft tissues inside your mouth, places where cold sores don't occur.

Cold sores are common. Though you can't cure or prevent cold sores, you can take steps to reduce their frequency and to limit the duration of an occurrence.

Signs and symptoms

Signs and symptoms of cold sores include:

  • Small, painful, fluid-filled blisters on a raised, red, painful area of your skin
  • Pain or tingling, called the prodrome, often precedes the blisters by one to two days
  • Usual duration of seven to 10 days

Cold sores usually appear on your lips. Occasionally, they occur on your nostrils, chin or fingers. And, although it's unusual, they may occur inside your mouth — but only on your gums or hard palate, which is the roof of your mouth. If the sore appears on other soft tissues inside your mouth, it may be a canker sore, but it's not a cold sore.

Signs and symptoms may not start for as long as 20 days after exposure to the herpes simplex virus, and usually last seven to 10 days. The blisters form, break and ooze. Then a yellow crust forms and finally sloughs off to uncover pinkish skin that heals without a scar.


Certain strains of the herpes virus cause cold sores. Herpes simplex virus type 1 usually causes cold sores. Herpes simplex virus type 2 is usually responsible for genital herpes. However, either type of the virus can cause sores in the facial area or on the genitals. You get cold sores from another person who has an active lesion. Shared eating utensils, razors and towels may spread this infection.

Once you've had an episode of cold sores, the virus lies dormant in the nerve cells in your skin and may emerge again as an active infection at or near the original site. You may experience an itch or heightened sensitivity at the site preceding each attack. Fever, menstruation, stress and exposure to the sun may trigger a recurrence.

When to seek medical advice

Cold sores generally clear up on their own without treatment. However, see your doctor if:

  • You have a pre-existing health condition that has compromised your immune system
  • The cold sores don't heal within one to two weeks on their own
  • Symptoms are severe
  • You have frequent recurrences of cold sores
  • You experience irritation in your eyes


Cold sores are contagious. They can pass from one person to another through skin-to-skin contact. The greatest risk of infection is from the time the blisters appear until they have completely dried and crusted over. There is a possibility of spreading the virus for some time even after the skin has healed.

If you have a cold sore, avoid close contact with infants, anyone who has eczema (atopic dermatitis) or people with a suppressed immune system, such as people with cancer, AIDS or an organ transplant. These people are at higher risk of more severe infection.

Herpes simplex infection of the eye causes scarring of the cornea and is a leading cause of blindness in the United States.


Cold sores generally clear up without treatment in seven to 10 days. If you experience frequent bouts, your doctor may prescribe an antiviral medication to treat cold sores. Using a medication may shorten the duration of cold sores and decrease your pain.


You can take steps to guard against cold sores, to prevent spreading them to other parts of your body or to avoid passing them along to another person:

  • Avoid kissing and skin contact with people while blisters are present. The virus can spread easily as long as there are moist secretions from your blisters. In persons with depressed immune systems, the virus can be spread even after the skin appears to be healed.
  • Avoid sharing items. Utensils, towels and other items can spread the virus when blisters are present.
  • Keep your hands clean. Wash your hands carefully before touching another person when you have a cold sore.
  • Be careful about touching other parts of your body. Your eyes and genital area may be particularly susceptible to spread of the virus.
  • Avoid triggers. If possible try to avoid or prevent conditions that stress your body, such as getting a cold or the flu, not getting enough sleep or staying in the sun for long periods of time without applying sunblock.
  • Use sunblock. Apply sunblock to your lips and face before prolonged exposure to the sun — during both the winter and the summer — to help prevent cold sores.


Cold sores generally clear up without treatment. In the meantime, the following steps may provide relief:

  • Use creams. Over-the-counter (OTC) creams can provide comfort, but don't expect them to speed healing.
  • Take an OTC pain reliever. These include aspirin, acetaminophen (Tylenol, others) and ibuprofen (Advil, Motrin, others). But don't give aspirin to children. Aspirin may trigger a rare but potentially fatal disorder known as Reye's syndrome.
  • Use cold or heat. Try applying ice or warm compresses to the blisters to ease the pain.
  • Let it heal. Avoid squeezing, pinching or picking at any blister.

March 13, 2006

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