What are they caused by?

One afternoon when you’re having your snack, you notice that there is a small area of your mouth that hurts. By the time you get to dinner, that area is really painful. You look in the mirror and notice a small ulcer in that area of your mouth. What caused it to form? How long will it be there? What can you do to make it go away?

0520   Canker Sores TNDefinition

Aphthous ulcers are what we commonly know as canker sores. These are small, shallow lesions that form in the soft tissues of your mouth and gums. The exact cause is unknown, but several factors are thought to play a role. One of the main reasons is a minor injury to the area, which is typically the result of having dental work done, accidentally biting your cheek or brushing/flossing too hard. Experiencing emotional stress is also thought to be a large contributor. Some other possible causes could be using toothpastes/mouth rinses that have sodium lauryl sulfate in them, certain food sensitivities, a diet low in vitamin B12/zinc/folate/iron, the hormonal shift brought on by menstruation, allergic response to the bacteria in your mouth or having certain conditions, like celiac disease, Crohn’s disease, ulcerative colitis and HIV/AIDS. Canker sores are not related to cold sores because they aren’t caused by the herpes virus and aren’t contagious. While anyone can develop canker sores, they are more common in teenagers/young adults, women and those who have a family history of canker sores.

There are three types with the most common being minor canker sores. They are usually small, round/oval shaped ulcers that have a white/yellow center with a red border. They are often painful and make it uncomfortable to eat or talk. Typically, they heal within one to two weeks and don’t usually leave a scar. Major canker sores are larger and deeper and can have irregularly shaped edges. These are extremely painful and might take six weeks to heal. They also can cause a significant amount of scarring to the area. Herpetiform canker sores, despite their name, are not related to the herpes virus but are pinpoint in size and often form in clusters, like herpes, that can combine into a single large ulcer. Since it’s a combination of many ulcers, the edges are usually irregular. Similarly, to minor canker sores, they heal in about one to two weeks without any scarring. Also, these type of canker sores form more often later in life.

TreatmentFast Facts Canker Sores

Most canker sores will heal on their own, so they don’t require treatment from a doctor. There are over-the-counter pastes, creams, gels and liquids that you can use to help relieve your pain and discomfort. Some of these products contain active ingredients, like benzocaine, fluocinonide or hydrogen peroxide. You can also rinse your mouth with a salt water or baking soda rinse. To do this, dissolve 1 teaspoon of either into ½ cup of warm water. Sucking on ice chips and letting them melt over the sores can help to reduce the pain. A key thing to avoid are food that can cause further irritation, such as those that are acidic, spicy or have sharp edges (ex. crackers). Be careful when brushing your teeth, so you don’t further damage the area. It can be a good idea to get toothpaste that doesn’t foam up. Also, avoid mouth rinses that contain alcohol. Some people get relief by putting a small amount of milk of magnesia on the sore several times a day because this provides a layer of protection.

You might need to see a doctor if you have large canker sores, especially if it lasts longer than two weeks, you can’t control the pain on your own, your having difficulty eating/drinking, new sores develop before the old ones heal, you have a fever, the sores extend into your lips or you have a sharp tooth or dental appliance that is causing the sores. If you have any of these symptoms, your doctor or dentist can prescribe medications that can help, such as prescription strength topical products, mouth rinses or pills. If you have frequent canker sores, your doctor or dentist can help determine the cause by doing specific tests to see if you’re deficient in any nutrients or have any other health problems. Also, if the sores are large, they can cauterize (burn) the tissue in order to destroy it using chemicals or an instrument.


There are things that you can do to help prevent canker sores from occurring. The main one is having good oral hygiene by regularly brushing and flossing. Just remember to use a soft brush and if you’re sensitive to toothpastes that contain sodium lauryl sulfate, avoid them. Another thing that can help is reducing the amount of stress that you’re under. Since some canker sores are caused by foods that irritate your mouth, take note if you experience canker sores after you eat certain foods so you can avoid them in the future. In addition, make sure you are getting enough fruits, vegetables and whole grains to avoid any nutritional deficiencies. If you have any dental appliances that are causing sores, talk to your dentist about options to decrease the level of irritation.

Canker sores are painful and annoying. The good news is that most of them go away on their own fairly quickly. If you have any questions or concerns about canker sores, please speak with your doctor or dentist. If you would like more information, please visit the American Academy of Oral Medicine’s canker sore page at https://www.aaom.com/index.php%3Foption=com_content&view=article&id=82:canker-sores&catid=22:patient-condition-information&Itemid=120