Canker sores are small shallow ulcers that occur in the lining of the mouth. The medical term for canker sores is “aphthous ulcers.” Canker sores start as white to yellowish ulcers that are surrounded by redness. They are usually very small (less than 1 mm) but may enlarge to ½ to 1 inch in diameter. Canker sores can be painful and often make eating and talking uncomfortable. There are two types of canker sores:
The exact cause of most canker sores is unknown. A stress or minor injury to the inside of the mouth is thought to be the cause of simple canker sores. Certain foods —including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, strawberries) — can trigger a canker sore or make the problem worse. Use of nonsteroidal anti-inflammatory drugs, like ibuprofen (Advil®, Motrin®), is another common cause. Sometimes a sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger the sores.
Some cases of complex canker sores are seen in patients with diseases of the immune system. These diseases include lupus, Behcet's disease, inflammatory bowel diseases (including celiac disease, ulcerative colitis and Crohn’s disease) and AIDS. Canker sores are also seen in patients with nutritional problems, such as a deficiency in vitamin B-12, zinc, folic acid or iron.
You may have a canker sore if you have:
In severe attacks, you may also experience:
No. Although these sores are often confused for each other, they are not the same. Cold sores, also called fever blisters or herpes simplex type 1, are groups of painful, fluid-filled blisters. Cold sores are caused by a virus and are extremely contagious. Canker sores are not caused by an infection and so are not contagious. Also, cold sores typically appear outside the mouth — usually, under the nose, around the lips or under the chin, while canker sores occur inside the mouth.
Pain from a canker sore generally lessens in a few days and the sores usually heal without treatment in about a week or two. Simple over-the-counter products, such as Kank-A®, Zilactin® or Orajel®, can be taken to ease symptoms.
Sores that are large, painful, or don’t heal before new ones appear may be treated with a prescription antibacterial mouth rinse, a corticosteroid ointment or a prescription or nonprescription solution to reduce the pain and irritation.
Although there is no cure for canker sores and they often recur, you may be able to reduce their frequency by:
You should call your doctor or dentist if you have:
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 08/29/2019