Lots of fruit and veg to keep your immune system healthy. Ulcers are usually a sign that your system is run down and you need a boost. I had a recurring mouth ulcer for a number of months and obtained a spray from the dentist called "CORSODYL ." It's a bit pricy, but really quickly effective - haven't had an ulcer since i used it, that was about two years ago. Incidently, the dentist told me that gels that are used in the mouth to treat ulcers are not usually effective, as they just slide off the affected area before they can take effect. Don't waste your money, get some corsodyl!!