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.
HSV-1 is a very common virus. It is thought that 90% of adults have been exposed to the virus during their lifetime.
Fever, cold temperature, ultraviolet sun light, sunburn, emotional stress, nerve injury, or abrasions can reactivate herpes simplex to cause cold sores.