I've had canker sores most of my life. I've even gone through the mayo clinic in Rochester Minnesota. They always told me to stop chewing gum and sucking on suckers. I found it didn't work. I've have found I only get canker sores during my menstrual cycle- about a week before. I have found I'm low on iron during that time . I have started taking iron supplements a has worked wonders- no more cankersores.