Who is affected by cold sores?

The virus that causes cold sores is common. Most people have been infected with this virus (herpes simplex virus, or HSV) by the time they reach adulthood.

Although most people have been exposed to HSV, only about 20% to 40% develop recurring cold sores.¹ After a person becomes infected, the virus remains inactive in the body until it is triggered by something such as sunlight exposure or stress. When active, the virus results in a cold sore outbreak.

Citations

1. Marques AR, Straus SE (2003). Herpes simplex. In IM Freedberg et al., eds., Fitzpatrick's Dermatology in General Medicine, vol. 2, chap. 214, pp. 2059–2070. New York: McGraw-Hill.