Canker sores are small ulcer craters in the lining of the mouth.  They are also known as Aphthous ulcers, Aphthous stomatitis, Aphthae.  They are frequently painful, recurring and sensitive. Canker sore is the most commonly seen lesion of the mouth. These oral lesions are grayish white, oval or round in shape having eroded surface and is surrounded by red inflamed area. They can occur singly or in groups. They can be small lesions or the large lesions. They are not contagious but have high recurrence rate.

Incidence and Frequency of Canker Sores:

Canker sores are very common. About 20% of the populations have canker sores at any one time. Their recurrence rate is high. They can reoccur around 3 to 4 times in a year. Frequency of recurrence of canker sores differs from person to person. In some persons, there is single or two episodes of canker sores a year, while in others there may be a continuous series of these sores.

Common Causes of Canker Sores:

No exact cause is known for canker sores. But the experts say that it can occur because of the following reasons:

  1. Bacterial infections: Hemolytic streptococcus and streptococcus sanguis has been detected in the  lesions of patients with canker sores.
  2. Immunological auto-antibodies formation to the spinous layer
  3. Iron, Vitamin B12 or folic acid deficiency: Nutritional deficiencies of iron, vitamin B12 or folic acid can also cause canker sores
  4. Hereditary

Precipitating Factors for Canker Sores: A number of conditions have been repeatedly identified immediately preceding the outbreak of canker sores in relatively large number of patients. These are:

  1. Traumatic episodes - Any irritation or injury from dentures or the sharp teeth
  2. Endocrinal conditions like pregnancy, menstrual period
  3. Psychogenic disorders
  4. Allergic reactions

Different Types of Canker Sores

On the basis of clinical features, Canker sores/ Aphthous stomatitis has been classified into three chief varieties. These are:

  1. Canker sore major ulcerations/Recurrent Aphthous ulcers major
  2. Canker sore minor ulcerations/Recurrent Aphthous ulcers minor
  3. Recurrent Herpetiform ulcerations

Canker sore major ulcerations/Recurrent Aphthous Ulcers Major

They are large sized painful ulcers which are mostly seen on keratinized mucosa that is the tongue, lips and cheeks. They can also occur on vagina, penis, rectum, anus, larynx with associated rheumatoid arthritis. They are 1-10 in number and healing occurs in 6 weeks with scarring.

Major Recurrent Aphthous Ulcer

Canker sore minor ulcerations/Recurrent Aphthous Ulcers Minor

 They are the most common ulcers. They are small in size about 0.5 cm and are most commonly found on the non-keratinized mucosa. They are 1-100 in number. The frequency of these ulcers varies. These ulcers are covered with grayish membrane and are surrounded by red inflammatory halo. There is no scarring on healing. Healing occurs in 7-14 days.  Histologic features of these ulcers are similar to major aphthae.

Minor Recurrent Aphthous Ulcer

Recurrent Herpetiform Ulcerations

These ulcers are extremely painful and occur in crops. These are multiple up to 100 in number and of pinhead sized initially but later may coalesce to form larger ulcers. These ulcers persist for years and heal without scarring. 

Herpetiform Aphthous Ulcer in Relation to Floor of the Mouth

Clinical features of Canker Sores:

  • Age: Canker sores can occur in people of any age group but it is more likely to occur in teenagers. Kids as young as of age 2 years can have canker sores.
  • Sex predisposition:  It is commonly seen in females as compared to males. It is seen two times more in women than men. Studies have shown that susceptibility to outbreaks of recurrent canker sores is inherited in some patients.
  • Site of occurrence of canker sores-They are normally found inside the mouth unlike the cold sores which are mostly seen outside the mouth. They can occur any where but most common sites are inner lining of the cheek, lip tongue and the roof of the mouth that is the soft palate.
  • Symptoms of canker sores- Canker sores start with a burning or tingling sensation and in a few days they form a red spot followed by an open ulcer which are very painful. They take around 7 to 10 days to heal. They are very sensitive to the spicy food otherwise they have self healing potential. Some times the secondary infection occurs then it requires antibiotics for the secondary infection.

Histological features of canker sores- Fibropurulent membrane covering over ulcerated epithelium is present. There is presence of acute inflammatory infiltrate in connective tissue. Granulation tissues are found at the base of ulcers. Anitskow cells are also found with elongated central chromatids in the nucleus.

Canker sores can be confused with-
Herpetic ulcers,
Traumatic ulcers

Prevention of canker sores:  Use of a non-alcoholic mouthwash reduces the chances of aphthous ulcers. Trauma due to braces is common cause of aphthous ulcers so brackets can be covered with wax to prevent injury to the oral mucosa in cases of patients with frequent occurrence of canker sores.

Treatment of canker sores: There is no treatment for canker sore and there is no treatment to stop the recurrence but there are ways to ease the discomfort. For that one can avoid irritating them. If the denture are causing irritation then that can be adjusted, if sharp teeth are there they can be rounded off. One should stay away from the spicy food. One can apply benzocaine ointment which can numb the area and there is temporary pain relief. Some times taking vitamin B 12 , folic acid and iron also helps. Using antiseptic mouth washes also helps. One can do rinses with that and it helps in healing and chances of secondary infection decreases. There is no specific treatment as the canker sores are self healing. They heal with in 7 to 10 days.


Treatment of canker sores with antibiotic treatment can lead to candidiasis. Rarely, bacterial infections such as cellulitis and Ludwig's angina may occur.

Canker sores are not cancer and don't lead to cancer. But if there is ulcer in the mouth and it is there for more than 2 weeks, then it is advised to consult a doctor.

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