Conditions InDepth: Cold Sores (Herpes Simplex Type 1)

Cold sores (fever blisters) are small, painful, fluid-filled blisters that occur on the lips, mouth, nose, chin, cheeks, and throat. They are most commonly caused by the herpes simplex type 1 virus (HSV-1). Less often, however, they can be caused by herpes simplex type 2 (HSV-2), the virus that most often causes genital herpes. Having a herpes simplex virus (HSV) infection around the mouth is very common. Nine out of ten older adults have been exposed to HSV, but not everyone who is exposed will develop cold sores.

Herpes Simplex on the Lips

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The virus can be spread by:

  • Contact with the fluid from a cold sore of another person through kissing and other close contact
  • Contact with the eating utensils, razors, towels, or other personal items of a person with active cold sores
  • Sharing food or drink with a person with active cold sores
  • Contact with saliva containing HSV

When HSV gets on the skin around the mouth, it invades nerves in the area. It then remains there, without causing symptoms, usually for 2-20 days, before the first (primary) outbreak occurs. This outbreak can cause blistering across the lips, tongue, and inside of the mouth. It may be accompanied by a body-wide, flu-like illness, consisting of fever, general aches and pains, and swollen lymph glands.

Once this outbreak is over, after about 7-10 days, the virus goes back into the nerves where it remains dormant until it is reactivated, causing another (secondary) outbreak. When this occurs, painful, blistering sores erupt, usually at the border of the colored part of the lip, and can last for up to 14 days. It is impossible to predict when these outbreaks may recur, but typically stress or illness may bring them on, as well as sunlight, immune suppressants, or a woman's menstrual period. Some people have outbreaks regularly, while some never have another.

What are the risk factors for cold sores?
What are the symptoms of cold sores?
How are cold sores diagnosed?
What are the treatments for cold sores?
Are there screening tests for cold sores?
How can I reduce my risk of cold sores?
What questions should I ask my doctor?
What is it like to live with cold sores?
Where can I get more information about cold sores?

References:

Beers MH, Fletcher AJ, et al. Merck Manual of Medical Information. 2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003.

Cold sore. Mayo Clinic website. Available at: http://www.mayoclinic.com/health/cold-sore/DS00358. Updated July 2008. Accessed September 24, 2008.

Herpes simplex. American Academy of Dermatology website. Available at: http://www.aad.org/default.htm. Accessed September 24, 2008.

Miller C. Oral herpes/cold sores essential facts. Australian Herpes Management Forum website. Available at: http://www.ahmf.com.au/oral_herpes/essential_facts.htm. Updated June 2007. Accessed September 24, 2008.



Last reviewed July 2008 by David Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.


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