Abstract: The present invention relates to the use of the nutrition supplement known as vitamin B12 (cobalamin) to treat or prevent mucosal lesions. It relates particularly to treatment of mucosal lesions and prevention of development of recurrent mucosal lesions by the repeated administration over a period of time of vitamin B12 where a subject has normal, or above normal, serum vitamin B12 levels. Compositions (medicaments), including friendly carriers (e.g. chewing gum), and kits, for vitamin B12 delivery to mucosal lesions or other injuries are also provided.