Once the cold sore has erupted, it will have to run its course. There is only one quick treatment for cold sores, and that is Valtrex, but unless you already have a prescription for it, it won’t work well for this cold sore. There is no over-the-counter medication or home remedy that cures cold sores, but Valtrex, which is an anti-viral medication, will make them go away much faster, and as a result of taking this medication you will have far fewer outbreaks of cold sores. It was intended for genital herpes, but cold sores are caused by the same family of viruses, and Valtrex stops colds sores in their tracks. None of the other treatments come close to the effectiveness of Valtrex, not the ointment Zovirax, and certainly not Abreva or anything else. Ask your doctor about it to see if you would be a good candidate for this medication.

Many of us already have the cold sore virus dormant in our bodies, and never have a flare up of cold sores. We contracted it as children, as it is a very common virus, and children pick it up easily as they often share food and drinks, and may be less concerned about hand washing and hygiene. Cold sores can be transmitted even when the person does not have a cold sore, though it is less likely to happen then.

These sites are informative.

http://www.webmd.com/skin-problems-and-treatments/tc/cold-sores-topic-overview
http://kidshealth.org/kid/ill_injure/aches/cold_sores.html
http://www.nlm.nih.gov/medlineplus/ency/imagepages/9325.htm