Can a cold sore heal without ever scabbing? if so, how do you know when it has fully healed?

Cold Sores: Cold sores are a herpes infection. You get such an infection from direct contact, such as kissing. Usually there is tingling of the skin followed by blisters which dry up, can scab, and then heal. Rarely, scarring may result. Unfortunately, there is no cure and the virus lives in the nerves forever. Therefore, the sores may come back--usually when under stress or there is sunburn.

Officially, "no": If a person has a history of cold sores, and there is a tingling spot on the lip (maybe slightly swollen and/or slightly reddened), and she quickly takes antivirals which stop the cold sore from fully developing, then it may go away without scabbing (it may peel slightly). Since the blisters did not form, the "cold sore" did not truly happen. If the sore fully developed, there would be scabbing.