What Causes Canker Sores in the Mouth?

Canker sores in the mouth have a variety of causes, including stress, nutritional deficiencies, and irritation from teeth or dental work. The consumption of certain foods, mouth injuries, and immune disorders or digestive tract illnesses may also be to blame. There may also be a genetic component to the development of canker sores. While they can be painful, canker sores in the mouth usually go away of their own accord and do not require medical treatment.

A canker sore is a mouth ulcer or lesion that can appear as a small open sore or blister. Canker sores in the mouth can be painful, and some people may mistake them for cold sores, also known as oral herpes. Canker sores and cold sores are two entirely different types of mouth sores. Canker sores are not contagious and are not caused by the herpes virus. Individuals with mouth sores should see their doctor or dentist for proper identification and diagnosis.


Any sort of oral trauma can result in a canker sore in the mouth. For example, over-vigorous tooth brushing or orthodontic appliances such as braces can result in mouth ulcers. In both cases, the canker sore is likely to go away on its own if the sufferer changes his brushing technique or as he gets used to his braces. Sometimes food allergies and sensitivities can trigger canker sores, particularly citrus fruits, chocolate, and coffee, as can sodium lauryl sulfate, an additive found in some oral hygiene products. Acidic and spicy foods can also further irritate existing canker sores in the mouth and slow their healing.

Some medical problems, particularly related to digestive or immune system disorders, can cause canker sores. Individuals with HIV/AIDS, irritable bowel syndrome, or celiac disease, for example, may develop canker sores, as may those who are undergoing chemotherapy. Hormonal changes, such as menstruation, can also cause canker sores in the mouth, as can stress or a deficiency in certain minerals as well as vitamin B-12.

Bacteria in the mouth, such as helicobacter pylori, which causes stomach ulcers, can also play a role in the development of canker sores. If canker sores do not go away on their own or they become very painful, doctors and dentists might prescribe topical painkillers. In more severe cases, mouthwashes containing antimicrobal agents or steroids might also be prescribed. Rarely, doctors might prescribe oral steroids or antibiotics, though the side effects of these medications can be unpleasant. In addition to medications, some doctors will also recommend vitamin supplementation to address vitamin deficiencies that may contribute to canker sores.



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