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Understanding Canker Sores

Canker sores (aphthous ulcers) are small, painful sores in the mouth. They occur most often on the tongue, gums, or insides of the cheeks.

What causes a canker sore?

The exact cause of canker sores is not known. But they are linked to different 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 often run in families.

What are the symptoms of a canker sore?

These are some common symptoms of canker sores:

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

  • Sores are often painful and sensitive to touch.

  • There may be a burning or tingling feeling 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 often go away by themselves within 10 to 14 days. There is no cure for canker sores. Treatment focuses on easing symptoms and shortening outbreaks. Treatments may include:

  • Prescription or other-the-counter topical treatments. These medicines are put right on the sores. Topical steroids may protect the canker sores from more 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 don't contain sodium lauryl sulfate. This type of toothpaste may prevent further aggravation of canker sores.

  • Oral prescription medicines. Oral medicines are taken by mouth. These are used for severe cases to help ease symptoms.

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

What are possible 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, talk with a healthcare provider. Canker sores can be so painful that they cause problems 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

Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Michael Kapner MD
Online Medical Reviewer: Ronald Karlin MD
Date Last Reviewed: 5/1/2016
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