Aphthous Ulcers (Recurrent Aphthous Stomatitis, Canker Sore)

Key Points

  • Recurrent aphthous ulcers are the most common oral ulcerative ailment, which classically appear as shallow, round or oval ulcers with an inflammatory edge and a faint pseudomembrane.
  • Diagnosis may be made by history and physical exam alone, but the presence of systemic symptoms may warrant a broad workup for potential underlying diseases manifesting with oral ulcers
  • Treatment is based on limited evidence and focused on symptomatic relief and decreasing ulcer duration, generally with local or topical analgesics or anti-inflammatory medications.


Aphthous ulcers are one of the most common diseases of the oral mucosa. Aphthous ulcerations (also called aphthae or canker sores) occur as shallow, rounded ulcers, with an inflammatory rim or halo, often with a pseudomembrane, which can fade from yellow/green to gray over time. The ulcers preferentially affect nonkeratinized mucosal surfaces, such as the labial or buccal mucosa, the sublingual mouth, or the tongue. Many patients suffer from recurrent lesions, termed recurrent aphthous stomatitis. The first lesions generally begin in childhood, and recurrent aphthous ulcers are more common in women, people under 40, Caucasian patients, nonsmokers, and people of high socioeconomic status. The disease usually remits in adulthood, after age 30. The true prevalence is difficult to say, as aphthous ulcerations are likely underreported; on average the prevalence in the US is estimated to be about 20%. Family history of disease is common. The diagnosis is generally made by history and physical exam alone, though the presence of systemic symptoms may prompt a more comprehensive investigation. A history of recurrent oral mucosal ulcers, generally starting in childhood, and the typical small round or oval ulcers on exam are key. There is likely an underlying genetic predisposition leading to immunologic abnormalities causing the inflammation in the oral cavity. Systemic and local factors may play a role as well, with deficiencies of vitamins (iron, vitamin B, folate), oral trauma, anxiety or stress, food sensitivities, and hormonal changes suggested as possible triggers in subsets of patients, though overall the data is conflicting and there is scarce evidence suggesting a specific cause.

The most common form of recurrent aphthous stomatitis is characterized by minor aphthous ulcers, which comprise about 80% of cases of recurrent aphthous stomatitis. These lesions are between 2 and 8 mm in diameter and heal over a 10- to 14-day period. Major aphthous ulcers are less common, making up 10-15% of cases, but often are more symptomatic and may require more aggressive treatment. Major aphthae are often one centimeter or more in diameter. A third type of aphthous stomatitis is termed herpetiform ulceration (although it is unrelated to herpes virus infection), and is characterized by multiple, pinpoint ulcerations. Approximately 80% of patients suffer from minor aphthae; major and herpetiform ulcerations are more likely to prompt patients to seek treatment, as they may last for weeks with significant discomfort.

Therapy for oral ulcerations is aimed at providing symptomatic relief and promoting ulcer healing. For major disease, systemic medications may diminish the duration or frequency of attacks.

There is an important differential diagnosis when evaluating patients with oral ulcers, even if the history and exam is strongly suggestive of aphthous ulcerations. The differential diagnosis can include oral involvement of inflammatory bowel disease, gluten sensitivity, Behçet’s syndrome, herpes simplex virus infection, other infections including syphilis, gonorrhea, coxsackievirus infection (hand-foot-mouth disease), and other herpes viruses (CMV, EBV, and VZV), HIV (including acute seroconversion), oral lichen planus, autoimmune blistering diseases, or drug eruptions. Any ulcer that lasts for more than three or four weeks requires evaluation to rule out other serious diseases, including local malignancies.