Canker Sore: 7 Main Causes (and What To Do)

A canker sore is small lesion that can occur on the mouth, throat or tongue, and that makes talking, eating, and swallowing uncomfortable.

It is not very clear what causes canker sores, however, some conditions can encourage the appearance of mouth sores, such as low immunity, intake of very acidic foods, or wounds caused by braces.  

Certain medications, stressful situations, and gastric disorders and acidity can also cause canker sores.

Canker Sore: 7 Main Causes (and What To Do)

Here we compile the main 7 causes for the appearance of canker sores and what to do in each situation:

1. Use of braces

It is common for mouth sores to appear when braces are put on. This is because it is common for there to be small traumas from the friction between the brace and the oral mucosa. Even though it causes great discomfort, it is not recommended to stop your dental hygiene. 

What to do: you should visit a dentist so that he can see if there is a link between the braces and the appearance of the canker sores. The doctor may recommend that you use protective wax on the braces and that you clean the lesion well, thus avoiding infections.

2. Nutritional deficiencies

Zinc, iron, folate, and vitamin B12 deficiencies can encourage the appearance of canker sores. 

What to do: to fulfill your body’s daily requirement for zinc, iron, folate, and vitamin B12 you should consume more foods of animal origin, such as meat, milk, and eggs, under the supervision of a nutritionist.

3. Genetics

When people within the same family have canker sores, it is probable that it is being caused by a genetic predisposition.

What to do: there is no way of controlling genetic factors, but there are ways of decreasing the chances of getting mouth sores, such as avoiding citrus fruits, such as pineapples, and spicy foods as they can irritate the oral mucosa and cause canker sores to appear. 

4. Biting your tongue or cheek

Biting your tongue or cheek can encourage canker sores to appear, which can make simple things like talking, swallowing, and chewing difficult and painful.

What to do: to take care of the canker sores, you can apply lotions on the affected area such as Triamcinolone Topical, or you can do a mouth rinse with Stryphnodendron tea as this plant has antiseptic and healing properties.

5. Psychological factors

Stress and anxiety can decrease your immune system’s action and thus increase your chances of infection. The oral mucosa can also dry out, which encourages canker sores to appear. 

What to do: it’s important to find ways of controlling stress and anxiety such as resting and doing physical activity.

6. Celiac disease

Celiac disease is a gastrointestinal disease characterized by an intolerance to gluten. Celiac disease does not cause canker sores, but the appearance of sores can be a symptom of the disease and, therefore, celiac disease should be investigated.

What to do: When the symptoms of celiac disease have been identified, it is important to go to a nutritionist for supervision on establishing a gluten-free diet. 


In addition to celiac disease, the appearance of mouth sores can be a symptom of AIDS. However,  canker sores are bigger, more frequent, and they take longer to heal with AIDS because the immune system is compromised.

What to do: In the first symptoms of AIDS, it is important to get supervision from an infectious diseases specialist or general practitioner so that treatment can be started immediately. 

When to go to the doctor

It is important to go to the doctor when:

  • The canker sores are large;
  • The appearance of mouth sores is very frequent;
  • The canker sores take a while to disappear;
  • Lesions start appearing on the lips;
  • The pain when swallowing or chewing does not pass even after taking analgesics.

When any of those symptoms appear it is important to go to the doctor so the cause can be identified and the treatment started, as the cause could be any number of serious conditions such as Crohns Disease, Irritable Bowel Syndrome, and even AIDS. 

How to eliminate canker sores definitively 

Canker sores usually disappear naturally in about a week or two. However, the use of home remedies can speed up healing. Some examples are: 

  • Mouth rinse with warm water and salt about 3 times a day, as salt has antiseptic properties, keeping the area clean and speeding up the healing. To make this remedy at home, simply add a teaspoon of rock salt to a glass of warm water and mix it well;
  • Place an ice cube on the canker sore to help relieve the pain and the inflammation;
  • Apply some honey on the canker sore using a cotton bud, as honey has healing properties.

Additionally, it is important to avoid eating acidic or spicy food while the canker sore has not disappeared, such as lemon, kiwi, and tomato. Also, rinse your mouth with an antiseptic mouthwash every day and maintain good daily hygiene.

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  • CENTRO DE INFORMAÇÃO DO MEDICAMENTO - ORDEM DOS FARMACÊUTICOS. Estomatite aftosa recorrente. Available on: <>. Access in 18 Apr 2019
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