Canker Sores

ExitCare ImageCanker sores are painful, open sores on the inside of the mouth and cheek. They may be white or yellow. The sores usually heal in 1 to 2 weeks. Women are more likely than men to have recurrent canker sores.


The cause of canker sores is not well understood. More than one cause is likely. Canker sores do not appear to be caused by certain types of germs (viruses or bacteria). Canker sores may be caused by:

  • An allergic reaction to certain foods.

  • Digestive problems.

  • Not having enough vitamin B12, folic acid, and iron.

  • Female sex hormones. Sores may come only during certain phases of a menstrual cycle. Often, there is improvement during pregnancy.

  • Genetics. Some people seem to inherit canker sore problems.

Emotional stress and injuries to the mouth may trigger outbreaks, but not cause them.


Canker sores are diagnosed by exam.


  • Patients who have frequent bouts of canker sores may have cultures taken of the sores, blood tests, or allergy tests. This helps determine if their sores are caused by a poor diet, an allergy, or some other preventable or treatable disease.

  • Vitamins may prevent recurrences or reduce the severity of canker sores in people with poor nutrition.

  • Numbing ointments can relieve pain. These are available in drug stores without a prescription.

  • Anti-inflammatory steroid mouth rinses or gels may be prescribed by your caregiver for severe sores.

  • Oral steroids may be prescribed if you have severe, recurrent canker sores. These strong medicines can cause many side effects and should be used only under the close direction of a dentist or physician.

  • Mouth rinses containing the antibiotic medicine may be prescribed. They may lessen symptoms and speed healing.

Healing usually happens in about 1 or 2 weeks with or without treatment. Certain antibiotic mouth rinses given to pregnant women and young children can permanently stain teeth. Talk to your caregiver about your treatment.


  • Avoid foods that cause canker sores for you.

  • 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.