Cold Sore Causes

The primary cause of cold sores is the herpes simplex type 1 virus. The virus is contagious and can be spread through direct skin-to-skin or mucous membrane contact and by sharing items that have come into contact with the cold sore (utensils, napkins, or drinks). While cold sores are generally associated with the type 1 virus, genital herpes is usually caused by the type 2 virus.

What Causes Cold Sores?

Cold sores are one of the most common conditions of the mouth. Also known as fever blisters (and known medically as herpes labialis), cold sores are caused by a contagious virus called the herpes simplex virus.
 
There are two types of herpes simplex viruses:
 
  • Herpes simplex type 1 (HSV-1)
  • Herpes simplex type 2 (HSV-2).
     
Most cases of cold sores are caused by HSV-1. In fact, more than 95 percent of recurrent cold sore outbreaks are caused by HSV-1. Most people infected with the HSV-1 virus usually become infected before they are 10 years old.
 
On the other hand, HSV-2 most commonly causes genital herpes (see Genital Herpes Causes).
 

Transmitting Cold Sores

One way that the herpes simplex virus is spread is by direct skin-to-skin or mucous membrane contact. For example, kissing a person with a cold sore is probably the most common way that cold sores are spread. The virus may also be spread by sharing things such as utensils, napkins, drinks, towels, or razors that have come in contact with the cold sore.
 
Children often become infected by contact with parents, siblings, or other close relatives who have cold sores. A child can spread the virus by rubbing his or her cold sore and then touching other children.
 
About 10 percent of oral herpes infections in adults result from oral sex with a person who has active genital herpes. These infections, however, usually do not result in repeat bouts of cold sores.
 
 

Cold Sore -- Information

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