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Pediatric - Mouth Ulcers

Mouth ulcers

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Canker Sore on Inner Lower Lip
Canker Sore on Inner Lower Lip

Chickenpox Sores in Mouth
Chickenpox Sores in Mouth

  • Painful, shallow ulcers (sores) on the lining of the mouth
  • The gums, the inner sides of the lips or cheeks are the usual sites.
  • Sores on the outer lips (e.g., recurrent fever blisters) are excluded


  • Canker Sores: The main cause of 1 or 2 ulcers after age 5
  • Hand-foot-mouth disease: The most common cause of multiple ulcers in the mouth, mainly on the tongue and sides of the mouth. It is common between ages 1 to 5 years.
  • Herpes Virus (Cold sore virus): The first infection can be severe and cause 10 or more ulcers on the gums, tongue and lips. Also, fever and difficulty swallowing. Usually occurs age 1 to 3.

Return to School

  • Canker sores are not contagious.  Children with fever or many mouth ulcers need to be examined before returning to day care or school.

If not, see these topics

When to Call Your Doctor

Call 911 Now (your child may need an ambulance) If
  • Not moving or too weak to stand
Call Your Doctor Now (night or day) If
  • Your child looks or acts very sick
  • Chemical in the mouth could have caused ulcers
  • Signs of dehydration (very dry mouth, no tears and no urine in more than 8 hours)
Call Your Doctor Within 24 Hours (between 9 am and 4 pm) If
  • You think your child needs to be seen
  • 4 or more ulcers
  • Bloody crusts on lips
  • Red, swollen gums
  • One ulcer on the gum near a tooth with a toothache
  • Fever or swollen face
  • Large lymph node under the jaw
  • Began after starting a medicine
Call Your Doctor During Weekday Office Hours If
  • You have other questions or concerns
  • Mouth ulcers last over 2 weeks
Parent Care at Home If
  • Probable canker sores and you don't think your child needs to be seen

  1. Canker sores are the #1 cause of mouth ulcers:
    • 1 to 3 painful, white ulcers of the inner cheeks or gums (no fever).
    • Causes include injuries from rough food, tooth brushes, biting, food irritants, etc.
  2. Liquid Antacid for Pain Relief:  
    • Use a liquid antacid 4 times per day for pain relief. (Some parents prefer regular mouth washes, but they may sting). 
    • Children over age 4 can use 1 teaspoon as a mouth wash after meals
    • For younger children, put ½ teaspoon in the front of the mouth after meals.
  3. Pain Medicine: Give acetaminophen (e.g., Tylenol) or ibuprofen for severe pain (especially at bedtime).
  4. Fluids :  
    • Offer a soft diet.  
    • Encourage favorite fluids to prevent dehydration. Cold drinks, milkshakes, and popsicles are especially good.  
    • Avoid salty foods, citrus fruits and foods that need much chewing.  
    • For infants, give fluids by cup, spoon or syringe rather than a bottle (Reason: The nipple can cause pain).
  5. Contagiousness: Canker sores are not contagious. Children with fever or many mouth ulcers need to be examined before returning to day care or school.
  6. Expected Course: They heal up in 1 to 2 weeks. Once they occur, no treatment can shorten the course, but treatment can reduce the amount of pain.
  7. Call Your Doctor If:
    • Mouth ulcers last over 2 weeks
    • Your child becomes worse

And remember, contact your doctor if your child develops any of the "Call Your Doctor" symptoms.

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: Barton D. Schmitt, M.D.

Last Reviewed: 1/19/2009

Last Revised: 9/2/2006

Content Set: Pediatric HouseCalls Online

Copyright 1994-2009 Barton D. Schmitt, M.D.

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