The short answer is that its not. In general, its best to wait until after the scabs and sores completely disappear before you kiss someone or engage in oral sex. This is because the herpes virus can continue shedding in the late stages of a cold sore healing, even if theres no viral fluid present.

Can cold sores spread without one?

Cold sores are caused by the herpes simplex virus type 1 (HSV-1). HSV-1 is very contagious. You can spread the virus even when you dont have any symptoms of a cold sore, though youre usually most contagious when you have them.