Cold sores are a symptom of the herpes simplex virus, which stays with a person for life and occasionally breaks out in the form of sores. If you or someone you know has cold sores, it's important to know whether or not they are contagious and when they are the most contagious.

The Virus Is Contagious

Cold sores, being a symptom of a virus and not a virus itself, are not what's contagious. The herpes simplex virus that causes sores is actually highly contagious. Many people actually get the virus at a very young age. While it can have devastating consequences for those with lowered immunity, it is largely an annoyance for most people and it lays dormant for much of the time. If you already have the virus, you can have an additional outbreak by coming into contact with someone else who's having an outbreak, so it makes sense to avoid contact when possible.

When the Virus Is Most Contagious

The herpes simplex virus is most contagious when a person has an outbreak, the symptoms of which are cold sores. So when you or someone you know has visible sores inside or outside of the mouth, the virus is in its most contagious phase. Sores are a good indicator of when you should take extra precaution not to spread the virus.

The herpes simplex virus is highly contagious and it's most contagious when an outbreak of cold sores is present. If you or someone you know has sores, take precautions not to spread the virus from person to person.