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What are canker sores?

A canker sore is a type of mouth ulcer — a break in the mucosal lining of the mouth

that exposes the sensitive tissue beneath. One canker sore may arise alone, or several sores may develop at once. Most canker sores are small, and they usually last less than 2 weeks.

Canker sores are most common in teenagers and young adults. Women suffer from canker sores more often than men; they seem to be especially susceptible just before a menstrual period.

What causes canker sores?

The cause of canker sores is unknown. People are most susceptible, however, when they are under stress, eating poorly, or run down due to illness or overwork. Nutritional deficiencies, particularly shortages of iron, vitamin B12, and folic acid, also predispose people to developing canker sores. Localized mouth trauma from burns, excessively vigorous tooth brushing, rough dental fillings, or dentures also set the stage for canker sores to develop.

How are canker sores diagnosed and treated?

Canker sores have a distinctive appearance, so a physician or dentist can diagnose them with a simple visual examination.

Treatment is aimed at relieving the pain and avoiding further mouth irritation until the sores heal.

What can I do myself?
Since the sores heal on their own in time, self-care is the best approach for most outbreaks of canker sores. A pharmacist can recommend over-the-counter lozenges or rinses that numb and protect the underlying tissue exposed by the ulcer, thus relieving pain.

Rinsing the mouth with a mild or diluted antiseptic mouthwash (full-strength mouthwashes may be too harsh) or warm salt water might also bring relief. In addition, avoid eating or drinking anything that triggers pain, such as hot, spicy, or acidic foods or beverages.

When should I see my doctor?
If mouth ulcers persist longer than expected, a doctor should be consulted to make sure they are canker sores. Recurrent canker sores should also be investigated.

What will the doctor do?
A doctor can prescribe an anesthetic mouthwash to be used a few hours before meals. This mouthwash anesthetizes the lining of the mouth and makes eating more comfortable. Alternatively, the doctor may prescribe a medicated paste to be applied to the sore area to ease discomfort and promote healing.

In cases of multiple, recurrent canker sores, a doctor may prescribe an antibiotic solution to hold in the mouth for a few minutes and then swallow. If this therapy is started early in the course of an episode, it can relieve pain within a day by coating the canker sores with a protective covering. This antibiotic rinse may also help prevent the development of future ulcers.

For the most severe attacks, a doctor may prescribe steroid medication in both mouthwash and pill forms.

The course of canker sores

Canker sores initially resemble shallow, oval lesions with slightly raised, yellowish borders. Within a week, they begin to resemble yellowish circles with borders. They can be stingingly painful, especially when the person eats or drinks something spicy or acidic, although the period of severe discomfort usually lasts only 3 or 4 days.

Canker sores develop on the soft, movable tissue within the mouth, generally inside the cheeks or lips. Only rarely do they develop on immovable tissue, such as the gums or palate.

Once a person has experienced a canker sore, repeated episodes are common, with several ulcers often occurring at once. Some unfortunate people may have as many as a dozen or more ulcers during an episode.

If the person has been infected by herpes simplex, which also causes mouth ulcers (called cold sores), they may tend to recur in conjunction with canker sores.

Are canker sores dangerous?
No, although they can be very uncomfortable and make eating difficult.