Canker Sores

Canker sores are painful, open sores on the inside of the mouth and cheek. They may be white or yellow. Canker sores are diagnosed by exam. There are many causes of canker sores. The cause of canker sores is not well understood. It may be caused by vitamin deficiency, hormonal changes, allergic reactions to certain foods, or digestive problems. The sores usually heal in 1 to 2 weeks.

Canker sores are less painful if you avoid foods that cause problems. You can also:

  • Avoid citrus juices, spicy or salty foods, and coffee until the sores are healed.

  • Use a soft-bristled toothbrush.

  • Chew your food carefully to avoid biting your cheek.

  • Apply topical numbing medicine to the sore to help relieve pain.

  • Apply a thin paste of baking soda and water to the sore to help heal the sore.

  • Only use mouth rinses or medicines for pain or discomfort as directed by your caregiver.


  • Your symptoms are not better in 1 week.

  • Your sores are still present after 2 weeks.

  • Your sores are very painful.

  • You have trouble breathing or swallowing.

  • Your sores come back frequently.