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Canker Sores: Causes, Symptoms and Relief

Canker sores, also known as aphthous ulcers or recurrent mouth ulcers or aphthous stomatitis, are shallow, open lesions (ulcers) that develop inside the mouth. These painful sores occur on the inner cheeks, base of the gums, inside lip, or on or under the tongue. Canker sores can make it uncomfortable to eat, drink and talk. They are very common, affecting about 20% of the population.

Though irritating and painful, canker sores are generally harmless. In most cases, they resolve spontaneously without any medical treatment within approximately two weeks. However, occasionally they may indicate an underlying medical condition. Canker sores are not contagious (though bacteria may build-up inside an ulcer leading to infection), but they often recur.

Types of Canker Sores

Based primarily on their size, canker sores can be divided into three different types, including:

Minor aphthous ulcers are the most common type of canker sores. These are small ulcers (less than 1cm in diameter) with a flat red border that may have a white, yellow or grey center. They usually leave no scars and heal within two weeks.

Major aphthous ulcers, also known as Sutton’s disease, are uncommon. These are large ulcers (greater than 1cm in diameter) with a raised red border. They may take up to a month to heal and leave scars.

Herpetiform ulcers is a rare type of cancer sore. These are clusters of tiny ulcers (each less than 3mm in diameter) that are otherwise similar to minor aphthous ulcers. They usually heal in about one week.

Causes and Risk Factors for Canker Sores

It is not exactly known why canker sores develop, but they appear to form due to an abnormal response by the body’s immune system in which white blood cells attack and damage tissue lining the mouth. This creates inflamed cavities known as canker sores. Although the exact cause is unclear, certain factors are believed to make a person more susceptible to canker sores. These factors include:

  • Family history. Canker sores appear to run in families.
  • Gender. Canker sores are more common in women than in men.
  • Age. Canker sores appear most often during adolescence and early adulthood though they may occur at any time in a person’s life.

In addition, certain factors seem to trigger an outbreak of canker sores, such as:

  • Tissue injury of the sensitive lining of the mouth may trigger canker sores. Examples include bites on the tongue, lip or inner cheek, sharp or broken teeth, ill-fitting dentures, braces and burns from hot foods or drinks.
  • Immune system deficiency may also trigger canker sores. Canker sores tend to appear when the body is busy fighting infections or in patients with HIV, AIDS or cancer.
  • Vitamin and mineral deficiency, particularly a lack of vitamins C, B12 and folic acid (B9) as well as a lack of minerals zinc and iron may be related to the onset of canker sores.
  • Allergic reactions may also trigger canker sores.
  • Stress and fatigue seem to contribute to the recurrence of canker sores.
  • Intestinal problems caused by certain digestive disorders, such as ulcerative colitis, Crohn’s disease or celiac disease, may trigger canker sores.
  • Hormonal changes. Canker sores tend to appear shortly before a menstrual period and disappear during pregnancy.
  • Side effects of medications, such as chemotherapy drugs or anti-inflammatory drugs (NSAIDs), may trigger the onset of canker sores.

Interestingly, despite general belief, smoking tobacco was not found to increase the risk of developing canker sores.

Symptoms of Canker Sores

Canker sores appear as a single sore or as a cluster of many sores on the inside of the mouth. They can develop on the inner cheeks, at the base of the gums, inside the lip and on or under the tongue. Canker sores are almost always painful. In fact, mouth ulcers that are not painful may be a sign of oral cancer.

Canker sores have a distinct appearance, i.e. they look like small, white, grey or pale yellow craters with red edges, they are round (circular in shape, not oblong), shallow and usually small (less than 1cm in diameter). Occasionally, symptoms such as fever, swollen lymph nodes or feeling ill may accompany canker sores.

A burning or tingling sensation in the mouth is usually the first sign of a developing canker sore. Within 6-24 hours, a red spot or bump appears. This bump bursts within a few days, leaving an open, shallow sore that enlarges. The pain of a canker sore usually subsides in the first few days, although the sores can last up to two weeks before healing spontaneously.

Certain symptoms may indicate an underlying medical condition such as connective tissue disease, inflammatory skin disorder, blood disease, drug reaction or cancer. When symptoms are too severe, prescription medications may be given to relieve them. Patients should know that symptoms such as extremely painful sores, fever, difficulty talking, chewing or swallowing, sores that are very large, recur frequently, have not healed after two weeks or appear to be spreading warrant medical attention.

Diagnosing Canker Sores

Canker sores can be usually identified through visual examination of the affected area in the doctor’s office. Rarely, additional tests, such as biopsy or blood tests, are required in order to help identify or rule out other potential conditions that can resemble or cause canker sores.

Canker sores are most commonly confused with cold sores. While cold sores are contagious, canker sores are not. They also differ in their cause (cold sores are caused by herpes simplex viruses), location (cold sores typically appear outside the mouth) and appearance (cold sores are blisters that burst and crust over).

Treatment of Canker Sores

Most often, canker sores heal on their own without medical treatment within two weeks. There is no available cure for canker sores. Thus, the goal of the treatment is to relieve the associated symptoms. Avoiding abrasive and spicy foods and acidic beverages that can irritate the inside of the mouth can help reduce the pain and discomfort. Some dentists recommend aloe vera to alleviate the pain of canker sores and speed up their healing. Ice can be applied to canker sores to numb the area and temporarily soothe the pain.

Over-the-counter as well as prescription medications may also be used to help relieve symptoms that accompany canker sores. Topical solutions such as mouth rinses and ointments are usually tried before use of systemic drugs. These medications may include:

Antimicrobial mouth rinses that fight infection by keeping the area clean.

Medications that coat the mouth, like those containing glycerine, may reduce pain by protecting existing sores from further irritation.

Carbamide peroxide is a combination of hydrogen peroxide and glycerine which cleans and protects the affected area.

Over-the-counter pain medications such as ibuprofen, acetaminophen (paracetamol) and aspirin may reduce inflammation and relieve pain. However, aspirin should not be given to children or teens.

Topical anesthetics can numb the area to help ease the pain.

Antacids, such as magnesium hydroxide solution, baking soda or wet tea bags, may be used to ease canker sore pain.

Hydrogen peroxide solution can be dabbed onto canker sores or used as a mouth rinse to inhibit the growth of bacteria in an ulcer.

In particularly severe cases, steroid medications or antibiotics may be prescribed. Canker sores may also be burned off with laser light to make them disappear completely within a few days.

It goes without saying that in case when an underlying condition is responsible for the canker sores, it is necessary to identify and treat that condition.

Preventing Canker Sores

There is no sure-fire way to prevent canker sores. They often recur in people who are prone to them. But, there are certain measures people can take to reduce the likelihood of an outbreak. These include maintaining generally good health, eating healthy diet to prevent nutritional deficiencies, practicing good dental hygiene, reducing stress and avoiding possible triggers and irritants.

Where to Find More Information: The American Academy of Oral Medicine