A.S.
Hello, I use to get the occasional fever blister on my mouth, too. ...I stumbled across this remarkable cream which actually cured me by accident because I have rosacea and had the cream on hand. If I feel the little sore coming up, then see it in the mirror - and this happens quite rapidly, what I use is hydrocortisone cream 1%. I put a lot of cream onto the arising sore and then if I wake up in the night I re-apply it generously. In the morning, it is virtually gone! Please consult your doctor about this. It is definitely worth you trying! Good luck.