When someone gets a cold sore or knows someone who has one, it is not uncommon for them to wonder, “Are cold sores contagious?” And the answer to this question is yes, cold sores are contagious in more ways than one. The herpes simplex virus that usually causes cold sores is easily spread--even if the infected person does not have an active cold sore.

Cold sores are contagious, and the HSV-1 virus that causes cold sores is present in an estimated 80% of the population. Most people are infected by HSV-1 at an early age, usually by the time they are five years old. Once the virus infects an individual, it will remain in that person’s body forever. Though HSV-1 is latent or dormant for much of the time, it is still present in the body. The virus is usually present near the person’s mouth, but it can spread all over the body. It is important to understand that an infected person can spread HSV-1 to others even while not currently experiencing an outbreak.

One of the most common ways that HSV-1 is spread is through an object an infected person used, like a toothbrush or tube of lip balm. If particles of the HSV-1 virus are transferred to an object and it is used by someone else, that person runs a strong risk of infection.

People are most likely to become infected by HSV-1 by exposure to someone with a cold sore. A cold sore goes through several phases before it disappears. The tingle stage is the first. At this point, the cold sore has not yet formed, but the virus has been reactivated. The risk of spreading the virus increases at this time, but the risk is highest when the sore is in the weeping stage. This is when the sore bursts open and expels a clear liquid. Even during the crusting stage, when the sore is scabbed over, the risk of infection is greater than normal.

It is important to note that HSV-1 can not only spread between people, but also to different parts of the infected person’s body. Herpetic whitlow, the HSV-1 infection of the fingers is particularly painful. People must be sure to wash their hands thoroughly when they have a cold sore to prevent the spread of HSV-1.