Canker Sores (Causes, Treatment, and Prevention)

Canker sores (aphthous ulcers or aphthous stomatitis) are small, painful ulcers inside the mouth. They may occur on the tongue and on the inside linings of the cheeks, lips, and throat. They usually appear white, gray, or yellow in color, with a red border.

Canker sores are among the most common types of oral lesions, affecting about 20% of people. Women get canker sores more often than men. Canker sore susceptibility may be inherited, and the condition can run in families.

Picture of a canker sore (aphthous ulcer)

Canker sores are not the same as cold sores (fever blisters), which are an infection caused by the herpes virus and are contagious. Canker sores are not contagious, and are categorized into three types:

1. Minor sores measure from 3 to 10 millimeters (mm) and are the most common type of canker sore. Lesions last 10 to 14 days and heal without scarring.
2. Major sores are larger and deeper than minor sores, have an irregular border, and a diameter of greater than 10 mm. Major canker sores may take weeks to months to heal and can leave a scar after healing.
3. Herpetiform sores are characterized by large groups of multiple sores. These are small ulcers (2-3 mm) but there may be as many as 100 ulcers present at the same time. They tend to heal without scarring.

The cause of most canker sores is not well understood, and multiple factors may cause sores to appear. Some possible causes of canker sores include the following:

• Injury to the mouth may cause simple canker sores. The injury could be from vigorous tooth brushing, dental work, braces or dentures, or a sports accident.
• Acidic foods, including citrus fruits, may trigger a canker sore or make it worse.
• Food sensitivities or allergies (anything from highly acidic foods to chocolate and coffee)
• Diets low in vitamins B12, zinc, folate (folic acid), or iron
• Toothpaste containing sodium lauryl sulfate
• Allergy to certain bacteria in the mouth
• Hormones
• Emotional stress
• Smoking
• Gastrointestinal tract diseases such as Celiac disease or Crohn's disease
• Autoimmune disorders such as systemic lupus erythematosus or Behçet's disease
• Other immune system weakness such as a cold or the flu, HIV/AIDS, or an organ transplant
• Systemic conditions such as Crohn's disease or nutritional deficiencies
• Oral cancer
• Certain drugs may cause canker sores, including:
  • Aspirin
  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Beta-blockers
  • Oral nicotine
  • Chemotherapy medicines
  • Immunosuppressants
  • Penicillamine
  • Sulfa drugs
  • Phenytoin
  • Anticholinergic bronchodilators
  • Platelet aggregation inhibitors
  • Vasodilators
  • Protease inhibitors
  • Antibiotics
  • Antiretrovirals
  • Antihypertensives

No, canker sores are not the same thing as fever blisters (cold sores).

Canker sores occur inside the mouth and are not contagious. Fever blisters are infections caused by the herpes simplex virus (HSV), they mostly occur on the lips and outside of the mouth, and they are very contagious.

Canker sores are painful sores inside the mouth. They may occur on the tongue, the lining of the cheeks, the gums, the inside of the lips, or the soft palate on the back of the roof of your mouth. Common symptoms of canker sores include the following:

• A burning, tingling, or prickling sensation, up to 24 hours before the sore appears
• Crater-like ulcers that are white, gray, or yellow in color, with a red border
• Sores are usually painful
• Difficulty speaking, eating or swallowing

Less common symptoms that can also indicate a more serious underlying infection include:

• Fever
• Swollen lymph nodes
• Sluggishness
• Weight loss
• Thrush infection in your mouth or throat

Contact your doctor or dentist if your canker sores are

• Larger than usual
• Spreading
• Lasting more than three weeks
• Causing severe pain even after taking over-the-counter pain medication
• Causing difficulty drinking enough fluids to stay hydrated
• Accompanied by fever

In most cases, canker sores do not require any treatment, and there is nothing specific you need to do to get rid of a canker sore because it usually will heal on its own. Home remedies can be used to help relieve the pain and inflammation of canker sores.

If you already have a canker sore, there are home remedies that can be used to help relieve the pain or irritation caused by the sore and to speed healing:

1. Topical medications applied directly on the sore, mouthwashes, and oral medications can relieve pain or inflammation.
2. Allow ice chips to dissolve slowly in your mouth for relief of pain.
3. Avoid acidic foods such as citrus fruits or spicy foods that may aggravate the sore.
4. If there is any vitamin deficiency (a doctor can test for this), take supplementation as prescribed.
5. Brush teeth gently and use a brush with soft bristles.
6. Use toothpaste and mouthwash that does not contain sodium lauryl sulfate.
7. Another home remedy is to mix milk of magnesia with Benadryl liquid and use it as a mouth rinse. You can also dab milk of magnesia directly onto the canker sore with a cotton swab.
8. Rinse your mouth with salt water or baking soda rinse. Mix 1 teaspoon of baking soda per ½ cup water, and rinse.
9. Other natural remedies include goldenseal mouth rinse, deglycyrrhizinated licorice (DGL) gargled in warm water, and saltwater rinses.
10. Zinc lozenges may help provide relief and speed healing time. Do not give lozenges to young children, as they may be a choking risk.
11. Vitamin C, vitamin B complex, and lysine can be taken orally when lesions first appear and may help speed healing.
12. Infuse sage and chamomile herbs in water and use as a mouthwash four to six times daily.
13. The herb Echinacea may help speed healing
14. Carrot, celery, and cantaloupe juices may also be helpful.

Consult a health care professional before using any home remedy as many have not been scientifically tested or proven effective.

Topical gels or ointments are used for canker sores to relieve pain, decrease inflammation, and prevent infection.

• Topical pain medications: Gels such as benzocaine (Orajel, Orabase) and lidocaine (an anesthetic) are used directly on the canker sore to relieve pain or discomfort. Canker sore patches (Canker Cover) provide pain relief while covering and protecting the sore as it heals. These types of medications can be found over the counter.
  Topical anti-inflammatory medications: Steroid medications such as triamcinolone acetonide or fluocinonide can be used topically to decrease inflammation from canker sores. These medications usually require a prescription and should be used exactly as your doctor or other health care professional has instructed.
• Topical antibiotics: These medications may be prescribed by your doctor or dentist if there is a possibility of the canker sore becoming infected with bacteria. Redness, crusting, pus discharge, or fever are signs of infection.

Several mouthwash solutions may be used to treat canker sore symptoms, and include:

• Diphenhydramine suspension (Benadryl Allergy liquid) is available over the counter and can be used as a mouth rinse because it has topical anesthetic effects on the tissue of the mouth and the canker sore. Put the suspension in your mouth, swish it around for 30 seconds to one minute, and spit it out. Do not swallow the rinse.
• Anti-inflammatory steroid mouth rinses may be prescribed to help reduce inflammation of the sores.
• Tetracycline antibiotic rinses may be prescribed and have been shown to relieve the pain and promote the healing of canker sores. Do not use tetracycline if you are pregnant, people allergic to tetracycline, or if the person with the canker sore is a child under 16 years of age.

Several oral medications may help relieve symptoms of canker sores.

• Over-the-counter pain medications such as ibuprofen (Advil), acetaminophen (Tylenol), or naproxen (Aleve) can be used to help with discomfort from canker sores.
• Zinc lozenges or vitamins B and C may also help relieve symptoms of canker sores.

• If a person suffers from frequent canker sores, there may be an underlying medical reason or illness that causes them. See a health care professional or dentist if there are any concerns that canker sores are frequent.
• Predisposition to canker sores may just be genetic. However, some diseases that affect the immune system such as lupus, Crohn's disease, celiac disease, or HIV/AIDS may cause frequent or recurrent canker sores.
• Health care professionals can order tests to determine if there is an underlying medical reason for a person's frequent canker sores.