The small, shallow ulcers that appear in the mouth and makes eating and talking uncomfortable are known as canker sores. Based on occurrence, there are two kinds of them:
1. Which appear three or four times a year and last up to a week. Typically, people of ages between 10 and 20 get them.
2. These are less common and occur more often in people who have previously had them.
Symptoms of Canker Sores
Canker sores are mostly round or oval with a white or yellow centre and a red border. They form inside the mouth- on or under the tongue, inside the cheeks or lips, at the base of the gums, or on the soft palate. 
A tingling or burning sensation might be experienced a day or two before the sores actually appear. Symptoms of canker sores may differ based on their types:
Minor Canker Sores- They are usually small, oval shaped, and heal without scarring in one or two weeks.
Major Canker Sores- They are less common, are larger and deeper than minor canker sores, have irregular edges, and may take up to six weeks to heal and can leave extensive scarring.
Herpetiform Canker Sores- These usually develop later in life, are pinpoint size, often occur in clusters of 10 to 100 sores, have irregular edges, and heal without scarring in one or two weeks.
When to See a Doctor for Canker Sores
Consult your doctor if you experience:
- Unusually large canker sores
- Recurring sores, with new ones developing before old ones heal
- Persistent sores, lasting three weeks or more
- Sores that extend into the lips themselves (vermilion border)
- Pain that you can't control with self-care measures
- Extreme difficulty eating or drinking
- High fever along with canker sores
Some people have sharp tooth surfaces or might be using dental appliances which can trigger canker sores. A dentist may help in this case.
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