Cause of canker sores unknown, but simple measures can provide relief

Young man with canker sore touching his mouth and grimacing in pain

The Medicine Cabinet: Ask the Harvard Experts  Q: I get canker sores about two to three times per year. Generally there is just one, but sometimes I have a couple at the same time. What causes them? Can they be prevented? A: A canker sore is a painful ulcers on the inside of the cheek […]