In an otherwise healthy person, cold sores are usually not contagious after the lesion has dried and crusted over. However, those who get recurrent cold sores may shed the virus (HSV-1) at times even when they do not have symptoms.
A cold sore is contagious for several days from before it erupts on the skin where it tingles, itches, or burns and to the time it bursts, scabs, and heals.
Cold sores usually last 7- 12 days long and are contagious at any stage. When the sore starts to weep is when you want to protect yourself and your significant other
The cold sores are very contagious when they are active. When they are very itchy. In a few days they become dried and crusted, the risk of contagious decrease.