Cankers!

Cankers! They are annoying, and seem impossible to predict or get rid of! Here's some light the Mayo Clinic shed on the issue! 

Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums. Unlike cold sores, canker sores don't occur on the surface of your lips and aren't contagious. They can be painful, however, and can make eating and talking difficult.

Most canker sores go away on their own in a week or two. Check with your doctor or dentist if you have unusually large or painful canker sores or canker sores that don't seem to heal.

When to see a doctor
Consult your doctor if you experience:

• Unusually large canker sores
• Recurring sores, with new ones developing before old ones heal
• Persistent sores, lasting three weeks or more
• Sores that extend into the lips themselves (vermilion border)
• Pain that you can't control with self-care measures
• Extreme difficulty eating or drinking
• High fever along with canker sores

See your dentist if you have sharp tooth surfaces or dental appliances that seem to trigger the sores.

http://www.mayoclinic.com/health/canker-sore/DS00354/DSECTION=symptoms