Canker Sore

Overview of Canker Sore

Canker sores are shallow, painful sores in the mouth. The cause is unknown but it is felt that stress or tissue injury can trigger or aggravate a canker sore. Other triggers may include poor nutrition, acidic foods, food allergies and menstruation. Canker sores are different from fever blisters, which usually are on the outside of the lips or the corners of the mouth. Unlike fever blisters, canker sores are not contagious.

Signs & Symptoms

  • Painful sore or sores inside the mouth – on the tongue, soft palate (back portion of the roof of your mouth), inside the cheeks or lips and at the base of the gums.
  • Tingling or burning sensation prior to appearance of the sores.
  • Sores that are round, white or gray in color with a red edge or border.
  • Severe attacks may be accompanied by fever, fatigue, swollen lymph nodes.


  • Avoid excessive abrasive, irritating foods including acidic or spicy foods.
  • Avoid irritation from gum chewing.
  • Brush your teeth with a soft bristled brush after meals and floss daily which will keep your mouth free of irritating foods.


The pain usually subsides in a few days without treatment. Sores are generally healed in 1 – 2 weeks without treatment. Call your doctor if the sores are unusually large, the sores are spreading or last longer than 2 weeks.

Self Care:

  • Over the counter pain medications such as acetaminophen.
  • Products such as anbesol, orajel, orabase, zilactin B, milk of magnesia applied directly to the sore.
  • Ice chips applied directly.
  • Salt water gargles.
  • Avoid abrasive, acidic or spicy foods.
  • Brush teeth with soft brush.

How We Can Help

  • If you would like to be seen by our medical staff, please contact our Appointment Desk to schedule an appointment.
  • Also, our Advice Nurse service is available at no charge for all UC Davis students to discuss health concerns and the need for medical care.