Canker Sore
A canker sore is a small painful ulcer inside the mouth. It is not contagious and usually heals on its own.
About canker sore
A canker sore is a small painful ulcer inside the mouth. It is not contagious and usually heals on its own.
What can cause it?
Canker sores may follow minor mouth injury, stress, illness, hormonal change, or sensitivity to certain foods or oral products.
Frequent or severe sores can be associated with nutrient deficiency, inflammatory bowel disease, celiac disease, or immune conditions.
What a patient may notice
Symptoms vary from person to person. Possible signs may include:
- Round or oval sore with a pale center
- Burning or tingling before the sore appears
- Pain with eating, drinking, or speaking
How clinicians find the cause
A clinician usually diagnoses the sore by examination and history. Blood tests or specialist evaluation may be needed for frequent, unusually large, slow-healing, or multi-site ulcers.
Treatment and next steps
- 1
Small sores usually heal within one to two weeks.
- 2
Protective pastes, numbing products, or prescribed anti-inflammatory rinses may reduce pain and duration.
- 3
Treatment of an underlying condition is needed when sores are recurrent.
Supporting recovery
- Choose soft bland foods, avoid spicy or acidic foods, and use a soft toothbrush.
- Rinse gently with salt water if comfortable and maintain hydration.
What to expect
Most canker sores heal without scarring. Pain often begins to ease within several days, while complete healing may take one to three weeks; larger ulcers may take longer. A sore that does not heal as expected should be examined because other mouth conditions can look similar.
Possible complications
- Reduced eating or drinking and dehydration when pain is severe
- Frequent or unusually large ulcers related to a nutritional, digestive, immune, or medication problem
- Delayed diagnosis of another condition when a persistent mouth ulcer is assumed to be a canker sore
When to Contact a Medical Professional
Mild symptoms may sometimes be managed with general supportive care, but a clinician should evaluate symptoms that persist, spread, become painful, or worsen.
Seek care for inability to drink, dehydration, very large or frequent sores, high fever, eye or genital sores, or sores lasting more than two weeks.Get emergency help for severe trouble breathing, new chest pressure, fainting, seizure, sudden weakness on one side, uncontrolled bleeding, blue or gray lips, or a person who is difficult to wake.
Ways to lower risk
- Avoid known food and toothpaste triggers and protect the mouth from sharp dental edges.
- Manage stress and maintain adequate nutrition.
Trusted health information
This CHS patient-education page uses original wording and links to MedlinePlus for additional information.