Canker sores (aphthous ulcers) are small sores inside the mouth. They are often found inside the lips, on the back part of the roof of the mouth (soft palate), inside the cheeks, or on the tongue.

Experts don't know the exact cause. But many factors are thought to play a role with how they happen. They include:

• Weakened immune system.
• Sensitivities to food, such as chocolate, cheese, nuts, and citrus fruits.
• Stress.
• Viruses and bacteria.
• Mouth injury.
• Poor nutrition and vitamin deficiencies.
• Certain medicines.
• Irritation from orthodontic braces.
• Hormonal changes.

Canker sores are often first seen in children and teens between ages 10 and 19. For about 3 in 10 children affected, canker sores come back for years after the first outbreak. They can't be spread from one child to another.

Canker sores that keep coming back may be linked to celiac disease, inflammatory bowel disease, or HIV infection.

Each child may feel symptoms a bit differently. Here are the most common symptoms of canker sores:

• Painful sores in the mouth, often inside the lips or cheeks, or on the tongue
• Sores that are white or gray with a red border
• Trouble eating or talking because of the sores
• No fever (in most cases)

Canker sores often heal in 7 to 14 days. They tend to come back.

Your child's doctor can often make a diagnosis with a full health history and a physical exam. But your child may also need these tests to rule out other causes:

• Blood tests
• Cultures of the sores
• Biopsy of the sore (taking a small piece of tissue from the sore and checking the cells under a microscope)

Treatment will depend on your child's symptoms, age, and general health. It will also depend on how severe the condition is.

The goal of treatment is to help ease symptoms. Treatment may include:

• Drinking more fluids.
• Taking acetaminophen for any fever or pain.
• Getting correct oral hygiene.
• Using medicines on the skin to help ease the pain of the sores.
• Using mouth rinses to help with the pain.

Your child may feel better by not eating spicy, salty, or acidic foods. These foods can make the mouth more irritated.

Contact your child's doctor if:

• The sores are very painful.
• The sores last more than a few weeks.
• The sores are very large in size.
• They keep coming back.

• Canker sores are small white or gray sores with a red border that are seen in the mouth.
• They are often found inside the lips, in the cheeks, or on the tongue.
• Experts don't know the exact cause. But they may be linked to things such as food allergies, stress, poor nutrition, or certain medicines.
• The sores are different from other sores. They are often diagnosed simply with a physical exam.
• Treatment may include oral medicine or medicine for the skin to ease pain. Antibiotics may be prescribed for secondary infections.

Tips to help you get the most from a visit to your child's doctor:

• Know the reason for the visit and what you want to happen.
• Before your visit, write down questions you want answered.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you for your child.
• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are and when they should be reported.
• Ask if your child's condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if your child does not take the medicine or have the test or procedure.
• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your child's doctor after office hours, and on weekends and holidays. This is important if your child becomes ill and you have questions or need advice.