In general, its best to wait for three to four days after the cold sore scab disappears 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.

How long after a cold sore are you contagious?

You are most contagious for two weeks after the cold sore initially appears, but because the virus lives in the body forever, it is always transmittable to others.