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Clinical Reference Systems: Pediatric Advisor 10.0

Canker Sores (Mouth Ulcers) (for Teenagers)


  • painful shallow ulcers (sores) in the lining of the mouth, usually on the inside of lips, inside of cheeks, and gums
  • no fever.


The exact cause of canker sores is not known. Some may result from prolonged contact with food that gets stuck in the teeth. Others may be due to forgotten injuries from toothbrushes, toothpicks, rough foods (such as corn chips), hot foods, or self-biting.

Herpes simplex causes recurrent fever blisters on the outer lip but does not cause recurrent canker sores on the inside of the mouth.


The white color of canker sores is the normal color of healing tissue in the mouth. They clear up in 1 to 2 weeks. Once they begin, no treatment can speed up the healing.


  1. Pain relief

    To reduce the pain, swish 1 teaspoon of an antacid solution in your mouth for several minutes. For a single sore, put an antacid tablet on the sore and let it dissolve. Do this three or four times a day. Take acetaminophen or ibuprofen as needed for pain (especially at bedtime).

  2. Diet

    Eat a soft, bland diet to reduce the pain. Cold drinks and milkshakes are especially good. Avoid salty foods, citrus fruits, and foods that need much chewing. Drink a lot of fluids to prevent dehydration.

  3. Prevention

    Canker sores tend to recur in some people. Good attention to toothbrushing after meals and dental flossing once a day may prevent some sores. Be careful with toothpicks and rough foods.

    Try to identify any foods that might be causing the ulcers. Were tomato, citrus fruit, peppermint, cinnamon, nuts, or shellfish eaten within the last day? If you find a food that you think may be causing the problem, don't eat the food for 2 weeks and then eat it again to see whether you get canker sores from it. If the canker sores do come back, never eat that food in the future.


  • The pain becomes severe.
  • You can't drink enough fluids.
  • The sores last longer than 2 weeks.
  • You feel the sores are getting worse.

Written by B.D. Schmitt, M.D., author of "Your Child's Health," Bantam Books.
Copyright 1999 Clinical Reference Systems