Abreva is meant to treat the herpes virus associated with cold sores. Mouth ulcers are aphthous ulcers and not associated with the H. virus. For internal cancer (mouth/aphthous) sores, I use aphthasol which is a prescription creme.
Like you I also have more cancer (mouth) sores while in a flare. If my Crohn's is under control, I rarely get them.
--40 year old female, dx as UC in '04 (1st symptoms in '03), switched to Crohn's in '05, 1 fistula, crohn's colitis, limited to large intestine
--rejected (reaction/didn't work): Asacol, AZA, 6-MP, MTX, Remicade, Humira, prednisone
--stuck on methylprednisolone, tried Prochymal in Phase III study (can't wait til it's approved!)
--started Tysabri 3/21/08
--single mom to 10-year-old girl