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Clinical Reference Systems: Pediatric Advisor 10.0
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Canker Sores (Mouth Ulcers)


  • 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. The sores clear up in 1 to 2 weeks. Once they begin, no treatment can speed up the healing.


  1. Pain relief

    To reduce the pain, your child can swish 1 teaspoon of an antacid solution in his or her mouth for several minutes. For very young children, put a half teaspoon of antacid solution directly on canker sores after meals. A child over age 4 with just one sore can put an antacid tablet on the sore and let it dissolve. Do this three or four times a day. Give acetaminophen or ibuprofen as needed for pain (especially at bedtime).

  2. Diet

    Offer a soft, bland diet to reduce the pain. Cold drinks and milkshakes are especially good. Avoid giving your child salty foods, citrus fruits, and foods that need much chewing. Encourage your child to drink favorite fluids to prevent dehydration. For very young children, give fluids by cup rather than from a bottle because the nipple can increase the pain.

  3. Prevention

    Canker sores tend to recur in some people. Good attention to toothbrushing after meals 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 let your child eat the food for 2 weeks and then offer it again to see whether your child gets canker sores from it. If the canker sores do come back, your child should never eat that food.


  • The pain becomes severe.
  • Your child can't drink enough fluids.
  • The sores last longer than 2 weeks.
  • You feel your child is getting worse.

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