L-lysine worked for me as well. During a cold sore, L-lysine kept the size of the sore down and made it go away quicker. After about six months of consistent dosage, I found I wasn’t getting them anymore. That was 20 years ago. If I get a cold sore once a year now, I’m “lucky”. When that happens, I dab on a teensy bit of peppermint essential oil as soon as I feel the tingle and it prevents the cold sore from ever popping up.