HealthSheets™


Understanding Canker Sores

Canker sores are small, painful sores inside the mouth. They occur most often on the tongue, gums, or insides of the cheeks. The medical term for canker sores is aphthous ulcers.

What causes a canker sore?

The exact cause of canker sores is not known, but they are linked to a number of conditions. These include:

  • An injury or irritation in the mouth, such as biting the inside of your cheek or braces rubbing

  • Allergy or sensitivity to certain foods or substances, such as citrus juice or some kinds of toothpaste

  • Poor nutrition

  • Emotional stress

  • Certain infections and illnesses

Canker sores tend to run in families.

What are the symptoms of a canker sore?

These are some common traits of canker sores:

  • Sores are open and grayish-yellow, surrounded by redness.

  • Sores are usually painful and sensitive to touch.

  • Canker sores may be preceded by a burning or tingling sensation a few hours to a few days before the sore appears.

  • Children and teens tend to get canker sores more often than adults.

How are canker sores treated?

Canker sores usually go away by themselves within 10 to 14 days. There is no cure for canker sores. Treatment focuses on relieving symptoms and shortening outbreaks. Treatments may include:

  • Prescription or over-the-counter skin treatments to apply to the sores. Steroids for your skin (topical) may protect the canker sores from further irritation and allow them to heal. Topical pain relief medicines may numb the area and make the sores less painful.

  • Certain types of toothpaste. These do not contain sodium lauryl sulfate. This type of toothpaste may prevent further aggravation of canker sores.

  • Oral prescription medicines. These are used for severe cases to help relieve symptoms.

  • Prescription or over-the-counter pain medicines. These help with discomfort.

What are the complications of a canker sore?

Mouth sores that seem to be canker sores can be signs of a more serious illness. If you have other signs of illness along with mouth sores, you should talk with a healthcare provider. Canker sores can be so painful that they interfere with talking, eating, or drinking.

When should I call my healthcare provider?

Call your healthcare provider right away if you have any of these:

  • Canker sores that don’t go away after 2 weeks

  • Canker sores that come back more than 3 times a year

  • Canker sores that are larger than about a half-inch across

  • Fever of 100.4°F (38°C) or higher, or as directed

  • Pain that gets worse

  • You aren’t able to eat or drink because of painful sores

  • Symptoms that don’t get better, or symptoms that get worse

  • New symptoms

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