Canker sores are bacterial, non-contagious infections that occur on the gums, inner lips, inside the cheeks and sometimes on the tongue. They are usually red and round with a white center. Most canker ...

Canker sores often seem to pop up out of nowhere and, once you have them, they’re often painfully hard to ignore — especially when you try to eat or even talk. So what, exactly, are canker sores? They ...