Cold sores — also called fever blisters — are a common viral infection. They are tiny, fluid-filled blisters on and around your lips. These blisters are often grouped together in patches. After the blisters break, a crust forms over the resulting sore. Cold sores usually heal in two to four weeks without leaving a scar.
Cold sores spread from person to person by close contact, such as kissing. They're caused by a herpes simplex virus (HSV-1) closely related to the one that causes genital herpes (HSV-2). Both of these viruses can affect your mouth or genitals and can be spread by oral sex. Cold sores are contagious even if you don't see the sores.
There's no cure for HSV infection, and the blisters may return. Antiviral medications can help cold sores heal more quickly and may reduce how often they return.
May 15, 2015
- AskMayoExpert. Cold sores. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2014.
- Habif TP. Warts, herpes simplex, and other viral infections. In: Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Edinburgh, U.K.; New York, N.Y.: Mosby Elsevier; 2010. http://www.clinicalkey.com. Accessed March 23, 2015.
- Herpes simplex. American Academy of Dermatology. https://www.aad.org/dermatology-a-to-z/diseases-and-treatments/e---h/herpes-simplex. Accessed March 23, 2015.
- Ferri FF. Herpes simplex. In: Ferri's Clinical Advisor 2015: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2015. www.clinicalkey.com. Accessed March 23, 2015.
- Herpes simplex virus (HSV) infections. The Merck Manual Professional Edition. www.merckmanuals.com. Accessed March 23, 2015.
- Cold sores. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed March 23, 2015.
- Wolff K, et al. Viral diseases of skin and mucosa. In: Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology. 7th ed. New York, N.Y.: The McGraw-Hill Companies; 2013. http://www.accessmedicine.com. Accessed March 23, 2015.
- Rakel RE. Dermatology. In: Textbook of Family Medicine. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.clinicalkey.com. Accessed March 23, 2015.
- Kliegman RM, et al. Herpes simplex virus. In: Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.clinicalkey.com. Accessed March 23, 2015.
- Klein RS. Treatment of herpes simplex virus type 1 infection in immunocompetent patients. http://www.uptodate.com/home. Accessed March 23, 2015.
- Gibson LE (expert opinion). Mayo Clinic, Rochester, Minn. April 6, 2015.
- Dorland's Illustrated Medical Dictionary. 32nd ed. Philadelphia, Pa.: W.B. Saunders; 2011. http://dorlands.com/index.jsp. Accessed March 25, 2015.
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