Sarah
I have found that fever blisters respond very well to an amino acid called L-Lysine. Most need 500 mg./day. Canker sores often respond well to Alum lumps held against them for a few minutes. It is very 'puckery' for those mnutes, but usually helps. You can find Alum in the spice section in the grocery; it is used in canning pickles, so is not harmful to hold the lump against the affected area for 15 min., or so. Good luck !