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Canker Sores (Mouth Ulcers)

What are canker sores?

Canker sores are painful shallow ulcers (sores) in the lining of the mouth, usually on the inside of lips, inside of cheeks, and gums. Your child will not get a fever from a canker sore.

What is the cause?

The exact cause of canker sores is not known. Some sores 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, food allergies, or self-biting.

Canker sores are not the same as cold sores. The herpes simplex virus causes cold sores (also known as fever blisters) on the outer lip. This virus does not cause canker sores on the inside of the mouth.

How long will they last?

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.

How can I take care of my child?

  • Pain relief

    Liquid Antacids: To reduce the pain, your child can swish 1 teaspoon of liquid antacid in his or her mouth for several minutes after meals. A child over age 6 with just one sore can put an antacid tablet on the sore and let it dissolve. Do this 3 or 4 times a day.

    Pain Medicines: Give acetaminophen (Tylenol) or ibuprofen (Advil) as needed for pain (especially at bedtime).

  • 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 spicy foods. Encourage your child to drink lots of fluids to prevent dehydration. For very young children, give fluids by cup rather than from a bottle because the nipple can increase the pain.

  • Prevention

    Canker sores tend to recur in some people. Using a soft toothbrush and brushing and flossing after all 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 try to avoid that food in the future.

When should I call my child's healthcare provider?

Call during office hours if:

  • The pain becomes severe.
  • Sores occur on the outside of the lips or mouth.
  • Your child can't drink enough fluids or refuses to eat.
  • The sores last longer than 2 weeks.
  • You feel your child is getting worse.
Written by Barton D. Schmitt, MD, author of “My Child Is Sick,” American Academy of Pediatrics Books.
Pediatric Advisor 2019.4 published by Change Healthcare.
Last modified: 2017-06-05
Last reviewed: 2018-07-13
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2018 Barton D. Schmitt, MD FAAP. All rights reserved.
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