What causes a canker sore?

The exact cause of canker sores isn't 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.

• An 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. Children and teens tend to get canker sores more often than adults. Canker sores aren't contagious.

What are the symptoms of a canker sore?

Common symptoms include:

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

• Sores that are often painful and sensitive to touch.

• A burning or tingling feeling a few hours to a few days before the sore appears.

How are canker sores treated?

Canker sores often go away by themselves within 7 to 14 days. There is no cure for canker sores. Treatment focuses on easing symptoms and shortening outbreaks. Treatments may include:

• Prescription or over-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 doctor. Canker sores can be so painful that they cause problems with talking, eating, or drinking.

When should I call my doctor?

Contact your doctor right away if:

• Your canker sores don’t go away after 2 weeks.

• Your canker sores come back more than 3 times a year.

• Your canker sores are larger than about a half-inch across.

• You have a fever of 100.4°F (38°C) or higher, or as directed by your doctor.

• Your pain gets worse.

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

• Your symptoms don’t get better, or they get worse.

• You have new symptoms.