L-lysine is an essential amino acid. It's been used to help control herpes virus (cold sores) outbreaks. Some studies have shown that it inhibits viral replication (when lysine levels are higher than arginine levels, so don't use an amino acid supplement with both). We were speculating that I might have some kind of viral infection (although I've never had a cold sore).
It might be that the Lysine plays a role in cellular repair or development. I'm guilty of not eating a lot of protein. It made a difference for me in a few days. It shouldn't be more than a few bucks. That plus the stress formula B-complex ought to be around $10.
I also used a moisturizer on my lips (under the vaseline). Exfoliate if you can, moisturize & let it soak in, then seal it in with the vaseline... Neutrogena "norwegian formula" hand cream works well, should be fairly hypoallergenic, and is also pretty inexpensive. It's hand cream, but it does say you can put it on your lips.