Canker Sore Symptoms, Causes & Treatment Options

Canker sores are benign but painful ulcerations in the oral mucosa. Symptomatic treatment can usually be achieved with home remedies or over the counter medications.

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  1. Overview
  2. Symptoms
  3. Potential Causes
  4. Treatment, Prevention and Relief
  5. When to Seek Further Consultation
  6. References

What Is A Canker Sore?


A canker sore (also known as an aphthous ulcer) is a painful, round ulcer with whitish-grey base, occurring on the oral mucosa. The exact cause of canker sores is unknown, though they are thought to occur as a minor auto-immune reaction. Canker sores are common and benign and occur most often in the second and third decades of life. They are often triggered by stress, illness, hormonal changes, poor oral hygiene, or certain foods or chemicals. Though canker sores will generally go away on their own within 1-2 weeks, a variety of treatments exist to decrease pain and speed healing, from home remedies to systemic immunosuppressive drugs. In certain cases, severe or recurrent canker sores may be related to underlying medical conditions or nutritional deficiencies. Canker sores can be prevented by avoiding known triggers, good oral hygiene, and general stress management. See a doctor if canker sores are severe and recurrent, or if home remedies fail to provide adequate pain relief.

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Canker Sore Symptoms

Main symptoms

Canker sores are a common, benign illness, and many people have experienced canker sores themselves. Some typical features of canker sores are listed below:

  • Painful: Pain and burning discomfort are the most common symptom of canker sores and are the reason they are noticed and treated. Pain and discomfort may precede the actual sore.
  • Sores: The sores themselves are generally round to ovoid-shaped shallow ulcerations with a white to grey base, surrounded by an intensely red ring.
  • Location: The vast majority of canker sores are located on the “nonkeratinized mucosa,” or the soft inner flesh of the mouth. This includes the labial (inside of lips) and buccal (inside of cheeks) mucosa, the bottom of the tongue, and the soft palate at the back of the mouth. Location is key in differentiating canker sores from herpes labialis infections, which tend to affect the keratinized skin at the outside border of the lips.
  • Size: Most normal canker sores will be less than 5 millimeters in diameter.
  • Duration: Most canker sores will last anywhere from 1-2 weeks.

More severe canker sores

In rare cases, more severe types of canker sores can occur. Several more severe types of canker sores are described below:

  • Major aphthae: In contrast to minor aphthae (normal canker sores), major aphthae are larger (generally greater than 1 centimeter in diameter) and last longer (can last up to 6 weeks). Major aphthae may occur anywhere minor aphthae can occur, plus several other locations like the hard palate, the top of the tongue, and the surface of the lips.
  • Herpetiform aphthae occur when many small lesions coalesce into one larger lesion. This may resemble a herpes labialis lesion but it is not actually caused by the herpes virus.
  • Complex aphthosis is defined as frequent outbreaks of multiple (3 or more) oral aphthae plus or minus genital aphthae. Complex aphthae are more likely to be related to underlying systemic conditions like Behcet’s disease, lupus, irritable bowel disease, HIV, or celiac disease.
  • Genital aphthae: The process that causes canker sores, or oral aphthae can also affect the soft mucosal tissue of the genitals in men or women, though this is much less common than oral ulceration [1].

Canker Sore Causes

Canker sores are an idiopathic condition, meaning that the exact cause of canker sores is still unknown. It is theorized that canker sores are caused by inappropriate activation of the immune system, and it is known that canker sores are not caused by an acute infection, and therefore are not contagious [2]. Canker sores are common and affect approximately 20% of the general population, with about 40% of those individuals suffering from recurrent canker sores. They occur most frequently in the second and third decades of life.

Though the cause of canker sores is not known, there are many known triggers for canker sores, which are described below:

  • Stress: a known trigger for canker sores and one of the most common
  • Trauma: for example, a burn or a bite on the inside of the mouth
  • Illness: stress-related and often connected with viral infections
  • Hormonal fluctuations: for example, menses
  • Allergies: One common set of allergies is additives in toothpaste and mouthwash. Foods can also cause allergy-related canker sores. Food triggers will vary by individual.
  • Quitting smoking: Interestingly, canker sores are less common among smokers and may begin after quitting smoking.
  • Poor oral hygiene can make canker sores more likely.

Associated conditions

Though the vast majority of canker sores are isolated occurrences, in select cases, canker sores may be related to an underlying systemic medical condition. Some of these conditions are described below:

  • Behcet’s disease: This disease causes recurrent canker sores with genital aphthous ulcers, without an alternative infectious cause.
  • Lupus: an autoimmune condition that affects many organ systems, which is best known for causing distinctive skin rashes. It can also cause complex or recurrent aphthae.
  • Crohn’s disease (or ulcerative colitis): Collectively known as irritable bowel disease, these conditions can cause repeated oral canker sores and genital aphthous ulcers. Their main symptoms are often gastrointestinal distress and bloody diarrhea.
  • HIV: The immune-deficiency causing virus may also cause severe, recurrent, or complex aphthae.
  • Celiac disease: Celiac disease is a digestive deficiency that causes gluten intolerance. It may be associated with increased oral ulcers.
  • Nutritional deficiencies: Deficiencies in vitamins and minerals are a preventable cause of severe or recurrent canker sores. Deficiencies in vitamins B12, B9 (folate), B6, B1 (Thiamine), B2, vitamin C, vitamin D, iron, and zinc are all possible causes of oral aphthae.

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Treatment Options, Relief, and Prevention for Canker Sores


Canker sores are not life-threatening and do not require treatment if none is desired. All of the treatments below exist to reduce the pain and discomfort of canker sores, and to possibly reduce their duration. There is no definitive cure for canker sores. Treatments are listed with milder treatments first, followed by more potent treatments.

Try these home remedies first to soothe the pain of canker sores:

  • Honey: to soothe the affected area
  • Saltwater: Gargle or wash with a saltwater solution to ease symptoms and potentially shorted the duration of the sore.
  • Baking soda solution: Gargle or wash with a solution of baking soda (bicarbonate) and water to ease symptoms and potentially shorted the duration of the sore.
  • Milk of magnesia [3]: This over-the-counter supplement may coat the sore to relieve pain.

If home remedies fail to provide relief, progress to the following treatment options:

  • Emollient paste (orabase): A specialized emollient paste designed for use in the mouth can provide pain relief and shield the sore from irritation.
  • Coating agents (bismuth subsalicylate, sucralfate): Coating agents can also help to shield sores from further irritation.
  • Topical analgesics (benzocaine): Topical analgesics, available in gels, sprays, and lozenges, can directly address the pain of canker sores.
  • Antiseptics: Antiseptic solutions like chlorhexidine gluconate and hydrogen peroxide can be used as mouthwashes to help speed the resolution of canker sores.
  • Antibacterial mouthwash: Antibacterial washes like tetracycline mouthwash can also help to speed healing and reduce inflammation [1].
  • Topical corticosteroids: Topical steroids like Clobetasol gel will help to reduce inflammation. Triamcinolone intralesional injection: Steroids like triamcinolone can also be injected directly into the sore in cases of severe agitation.

Finally, in cases of severe, complex, or recurrent canker sores that are refractory to the treatments listed above, the following options are available:

  • Test and replete nutrient levels: Because nutritional deficiencies can cause canker sores, levels of B, C, and D vitamins plus iron and zinc should be tested and repleted if low.
  • Workup for underlying disease: Testing for HIV, celiac disease, irritable bowel disease, and lupus may be necessary if recurrent, severe canker sores occur alongside other symptoms suggestive of these conditions.
  • Immune system modulation: In the most severe cases of canker sores, systemic drugs may be given to suppress the immune system. Some possible treatments include colchicine, dapsone, thalidomide, montelukast, methotrexate, and systemic steroids.


There are many good strategies that can help to prevent canker sores:

  • Good oral hygiene
  • Prevent oral trauma
  • Avoid known allergic triggers: This may mean changing to a toothpaste or mouthwash without the triggering ingredient or avoiding certain foods.
  • Good nutrition: A balanced diet or multivitamin can generally prevent nutritional deficiencies that may lead to canker sores. See a doctor and consider additional supplementation if you suspect nutritional deficiencies.
  • Stress management: Though it is not always easy to do, stress management may help to prevent stress-related canker sores.

When to Seek Further Consultation for Canker Sores

Most canker sores are painful, yet harmless and can be treated at home with home remedies or over the counter medications. See a doctor if you are unable to achieve adequate relief at home, and would like to pursue more potent treatments. Sometimes canker sores occur in relation to a more serious medical condition. See a doctor if you notice any of the following:

  • Large sores: greater than one centimeter in diameter
  • Location: sores on the top of the tongue, hard palate, lips, genitals, or eyes, or outside of the mouth
  • Duration: persistent sores lasting more than two weeks
  • Fever: sores accompanied by fever
  • Additional symptoms: You should see a doctor if canker sores are accompanied by bloody diarrhea, bowel movement changes, or gastrointestinal distress [4].