I remember reading that, when you give up smoking, mouth ulcers can be a problem. Scarily, it seems that the ciggies actually kill the bacteria in your mouth that cause them. When you give up smoking, therefore, you no longer kill the bacteria with smoking and need to find other ways of doing so. A friend of mine swilled her mouth out about twenty times a day with a really strong salt solution. It was three table spoons of salt to a glass of warm water. Her ulcers stopped after about six weeks.