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Canker Sores or Recurrent Aphthous Stomatitis (RAS) : Causes, Signs, Symptoms, Treatment

Canker Sores or Recurrent Aphthous stomatitis (RAS), medically termed as aphthous ulcers, are small and shallow ulcers or lesions, which develop in your oral cavity, commonly at the base of your gums or in the soft tissues of the mouth. Canker sores differ from cold sores in that they are not contagious and do not develop on the lips’ surface. Canker sores can be painful and the patient may have difficulty in talking and eating.

Canker Sores or Recurrent Aphthous Stomatitis (RAS)

Majority of the Canker Sores or Recurrent Aphthous Stomatitis (RAS) resolve on their own within 10 days or so. If the canker sores do not heal and are large in size or are very painful, then they require medical attention. Treatment comprises of mouth rinses, topical applications and steroid medications.

Causes of Canker Sores or Recurrent Aphthous Stomatitis (RAS)

The exact cause of Canker Sores or Recurrent Aphthous Stomatitis is not clear. According to experts, combination of various factors causes canker sores. Triggering factors for Canker Sores or Recurrent Aphthous Stomatitis are:

Risk Factors for Canker Sores or Recurrent Aphthous Stomatitis

  • Being a woman increases the risk for developing canker sores.
  • Having a family history of canker sores increases the risk for having them.

Signs and Symptoms of Canker Sores or Recurrent Aphthous Stomatitis

  • Majority of the canker sores are oval or round shaped with a yellow or white center surrounded by a red border.
  • They are found in the mouth, on the surface of the tongue, under the tongue, inside of the cheeks, base of the gums, lips and soft palate.
  • Patient may experience a burning/tingling sensation a couple of days before the appearance of the sores.

Symptoms Requiring Medical Attention Include:

  • Canker sores which are exceptionally large in size.
  • Recurrent sores, where new canker sores develop even before the old ones have healed.
  • Sores which spread into the lips themselves (vermilion border).
  • Sores which do not heal and persist beyond three weeks or more.
  • Persistent pain.
  • Difficulty in drinking or eating.
  • High grade fever.
  • If you have sharp tooth cusps or surfaces or if there are any dental appliances, such as braces, which are causing the canker sores; then you need to consult your dentist regarding them.

Types of Canker Sores or Recurrent Aphthous Stomatitis

  • Major Canker Sores appear less commonly than minor canker sores. They are bigger in size and deeper than the minor canker sores. They are found to have irregular borders and time taken for them to heal is around 5 to 6 weeks with deep scarring.
  • Minor Canker Sores are the commonest type. They are often small in size, oval in shape and heal within a week or two without scarring.
  • Herpetiform Canker Sores commonly develop later in life and they are pin point in size. They typically develop in clusters of 10 to 100 sores. They have irregular borders and heal without scarring within a week or two.

Investigations for Canker Sores or Recurrent Aphthous Stomatitis

There aren’t any specific investigations or tests required for diagnosing canker sores. Visual exam is sufficient for diagnosis. For persistent and severe sores, some tests will be conducted to rule out other medical problems.

Treatment for Canker Sores or Recurrent Aphthous Stomatitis

Treatment is not usually required for minor canker sores, as they resolve on their own within a couple of weeks. Large, painful or persistent sores, on the other hand, need treatment which comprises of topical ointments, mouth rinses and systemic corticosteroids for severe canker sores.

  • Mouth rinses, which have the steroid dexamethasone, are prescribed for multiple canker sores. This will help in relieving inflammation and pain.
  • OTC, as well as prescription topical pastes, which contain active ingredients like benzocaine, amlexanox and fluocinonide help with the pain and encourage the healing process. They need to be applied to individual sores about three to four times a day as soon as they appear and till they heal.
  • Oral steroid medications are prescribed for severe canker sores, which are not responding to other treatment options. However, they have some serious side effects and should be used with extreme caution and under the doctor’s guidance.
  • Cauterization of the sores with chemical or via instrument can be done to destroy or burn the tissue.
  • Nutritional supplements are prescribed if the patient follows a diet which lacks vital nutrients like folate, vitamin B-6, vitamin B-12 and zinc.
  • If the cause of the canker sores is some other serious medical problem, then treating that underlying medical condition resolves the sores.

Home Remedies for Canker Sores or Recurrent Aphthous Stomatitis (RAS)

  • Over-the-counter numbing agents, such as benzocaine can be tried.
  • Rinse the mouth with a mixture of salt water or 1 teaspoon of baking soda in half a glass of warm water also helps.
  • A small amount of milk of magnesia can be applied to the canker sores for 3 to 4 times a day.
  • A paste of baking soda made with water applied to the canker sores helps with their healing.
  • Acidic/spicy/abrasive foods should be avoided as they can further irritate the sores and increase the pain.
  • Ice application to the canker sores helps with the pain and inflammation.
  • Always brush your teeth gently with a soft bristled toothbrush and use toothpaste which does not have foaming agents.

Prevention of Canker Sores or Recurrent Aphthous Stomatitis (RAS)

  • Try to follow a healthy diet comprising of fruits, vegetables and whole grains to prevent nutritional deficiencies.
  • Avoid foods which irritate the mouth, such as chips, nuts, pretzels, spicy/salty foods and acidic fruits.
  • Avoid chewing and talking at the same time, as this could result in a trauma to the oral cavity or a cheek/tongue bite.
  • It’s important to follow good oral hygiene, such as brushing after meals and flossing daily.
  • Consult your dentist if you have braces etc. for orthodontic waxes to cover the sharp edges.
  • Avoid stress by meditating and exercising regularly.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:September 2, 2023

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