Where Do Canker Sores Come from?

Canker sores are painful sores inside the mouth. Stress, minor injury to the inside of the mouth, acidic fruits and vegetables, and hot spicy foods can trigger the development of canker sores.

Are canker sores a virus?

Unlike cold sores, canker sores don't occur on the external surface of your lips (outside the mouth). "Even though canker sores and cold sores can have the same triggers, canker sores are not contagious," says Dr. Varinthrej Pitis. "There is no virus or bacteria associated with them.

What is the white stuff in canker sores?

Canker sores are small painful lumps that can grow on the lips or inside the mouth. These tiny swellings contain a mixture of WBCs (white blood cells) and bacteria, and some other fluids and look like white-yellowish cysts with a red border.