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Causes

By Mayo Clinic staff

Cold sores are caused by certain strains of the herpes simplex virus (HSV). HSV-1 usually causes cold sores. HSV-2 is usually responsible for genital herpes. However, either type can cause sores in the facial area or on the genitals.

You get the first episode of herpes infection from another person who has an active lesion. Shared eating utensils, razors and towels, as well as kissing, may spread HSV-1. Oral sex can spread HSV-1 to the genitals and HSV-2 to the lips.

While cold sores are most contagious when they are oozing fluid, the virus can be transmitted to others even during times when you have no blisters.

Once you've had an episode of herpes infection, the virus lies dormant in nerve cells in your skin and may emerge again as an active infection at or near the original site. Recurrence may be triggered by:

  • Fever
  • Menstruation
  • Stress
  • Fatigue
  • Exposure to the sun
Risk factors Symptoms
References
  1. Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Edinburgh, U.K.; New York, N.Y.: Mosby Elsevier; 2010. http://www.mdconsult.com/books/about.do?about=true&eid=4-u1.0-B978-0-7234-3541-9..X0001-6--TOP&isbn=978-0-7234-3541-9&uniqId=230100505-57. Accessed March 9, 2012.
  2. Herpes simplex. American Academy of Dermatology. http://www.aad.org/skin-conditions/dermatology-a-to-z/herpes-simplex. Accessed March 9, 2012.
  3. Ferri FF. Ferri's Clinical Advisor 2012: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/about.do?about=true&eid=4-u1.0-B978-0-323-05611-3..C2009-0-38601-8--TOP&isbn=978-0-323-05611-3&uniqId=291436269-101. Accessed March 9, 2012.
  4. Klein RS. Clinical manifestations and diagnosis of herpes simplex virus type 1 infection. http://www.uptodate.com/index. Accessed March 9, 2012.
  5. Kliegman RM, et al. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/208746819-6/0/1608/0.html. Accessed March 9, 2012.
  6. Goldman L, et al. Cecil Medicine. 24th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/191371208-2/0/1492/0.html#. Accessed March 9, 2012.
  7. Klein RS. Epidemiology of herpes simplex virus type 1 infection. http://www.uptodate.com/index. Accessed March 16, 2012.
  8. Wolff K, et al. Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology. 6th ed. New York, N.Y.: The McGraw-Hill Companies; 2009. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=45. Accessed March 16, 2012.
  9. Klein RS. Treatment of herpes simplex virus type 1 infection in immunocompetent patients. http://www.uptodate.com/index. Accessed March 16, 2012.
  10. Cold sores. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed March 19, 2012.
  11. Rakel RE. Textbook of Family Medicine. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/191205553-4/0/1481/0.html#. Accessed March 19, 2012.
DS00358 May 23, 2012

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