The medicines that have been proven to work on cold sores are called antivirals, and they work to stop a virus from replicating. This, in turn, can stop the cold sore from developing or may reduce its size and healing time. Antiviral medications are only available with a prescription. Cold sore antivirals come in two different forms:
topical medication (cream) that is applied directly to the area
oral medications (pills) that are taken by mouth