Keep in mind that the herpes virus that causes cold sores is very different from the one that causes the sexually transmitted form of the disease.

In fact, the majority of people have the cold sore kind -- it's frequently passed from parent to child. Just because you never had an outbreak doesn't mean you are not infected. The more benign form associated with cold sores often lays dormant, sometimes for peoples' whole lives.

Still, not cool to smoke with people when you have a cold sore.