Do you know that castor oil is also good for mouth ulcer? I only found it out few years ago. I get ulcer almost every month. Any small bite on the inner cheek can develop into a painful ulcer that won't go away on its own (my GP said it would but no it didn't). Every time I see an ulcer is appearing, I would gently dab very little amount of castor oil on the ulcer using my finger. I do this once or twice daily. In two or three days, the ulcer will be gone. If it's a big ulcer, I would dab it as often as possible every day (especially when it feels like burning in my mouth). In three or four days, it will be gone.