Aphthous Stomatitis

What Is It, Symptoms, and More

Author: Lily Guo

Editors: Alyssa Haag,Emily Miao, PharmD

Illustrator: Jessica Reynolds

Copyeditor: David G. Walker

Modified: 1 Mar 2022

What is aphthous stomatitis?

Aphthous stomatitis, also known as a canker sore, refers to small, painful ulcers that can appear on the inside of the lips, cheeks, or soft palate; on the floor of the mouth; on the gingiva of the teeth; or on the tongue. They typically only form on non-keratinized oral mucosa, which is the cell layer that lines the inner oral cavity. This is in contrast to ulcerations from herpes simplex virus (HSV), also known as cold sores, which affect the keratinized mucosal surfaces, such as the outer surfaces of the lips. Unlike cold sores, canker sores are non-contagious. 

Aphthous stomatitis affects 20% of the population and is more common in individuals assigned female at birth. They tend to occur most often in the second and third decades of life and become less common with advancing age.

What causes aphthous stomatitis?

The exact cause of aphthous stomatitis is not currently known; however, there are many factors that are thought to contribute, including a weakened immune system; emotional or psychological stress; certain foods, such as coffee, chocolate, cheese, nuts, and citrus fruits; trauma to the mouth; viral and bacterial infection; poor nutrition; and certain medications, such as aspirin, beta-blockers, chemotherapy medicines, penicillamine, sulfa drugs, and phenytoin. Sensitivity to ingredients in toothpaste and oral hygiene products, like sodium lauryl sulfate, may also trigger a canker sore. Other suspected causes include exposure to toxins (e.g., nitrites in drinking water), menstruation, or alterations in the oral microbiome. As many as 20% of cases can be related to deficiencies in iron, folate, and vitamin B6 and B12, although other deficiencies, such as vitamin D, zinc, or thiamine, may also be involved. 

Canker sores may also occur as a result of diseases, such as celiac disease, which is a gastrointestinal disorder caused by a sensitivity to gluten, a protein found in most grains. Celiac disease is present in fewer than 5% of recurrent aphthous stomatitis cases. They can also occur as a result of inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. Lastly, Behcet's disease (a rare disorder that causes inflammation throughout the body, including the mouth) can predispose an individual to canker sores.

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What causes recurrent aphthous stomatitis?

Recurrent aphthous stomatitis can be caused by exposure to certain foods that have been known to trigger onset of canker sores. It is best to avoid those foods that irritate the mouth and to consume a well-balanced diet of fruits, vegetables, and whole grains in order to prevent nutritional deficiencies. If the canker sore seems to be related to stress, using stress-reduction techniques, such as meditation and exercise, may help. Aphthous stomatitis is usually first seen in children and adolescents from the ages of 10 to 19 years. For about one-third of the children affected, lesions continue to reappear for years after the initial outbreak. Often those with recurrent canker sores have a family history of the disorder, which may be due to heredity or to a shared factor in the environment, such as certain foods 

What are the signs and symptoms of aphthous stomatitis?

The signs and symptoms of aphthous stomatitis include feeling burning or discomfort in the oral mucosa a day or two before the onset of ulcerations. Fever, rash, headache, or lymphadenopathy are typically absent. The ulcer initially presents as a pinpoint papule over the course of 1-2 days, then gradually expands to its maximal size over 3-4 days before it stabilizes then heals. They are commonly localized to the inner lips, on the inside of the cheeks, and on the tongue. They are typically well-circumscribed and can be minor, major, or herpetiform in morphology. 

Minor aphthous ulcerations, the most common form of aphthous stomatitis, are less than 1 cm in diameter, round or oval in shape, with yellow or gray pseudomembrane (i.e., a layer of dead cells that can be wiped off). The ulcer is typically surrounded by an inflammatory red halo and usually heals within 7-14 days. 

On the other hand, major aphthous ulcers are deeper, larger (i.e., often 2-3 cm in diameter), can have irregular raised borders, and typically take many weeks or months to heal. They can subsequently result in scarring. 

Lastly, the least common form are herpetiform recurrent aphthous ulcers, which consist of multiple ulcers that cluster in groups of 10 to 100 throughout the mouth and are 1 to 2 mm in diameter. They can sometimes coalesce into larger ulcers and they usually heal within a few weeks.

How is aphthous stomatitis diagnosed?

Aphthous stomatitis is usually diagnosed based on a complete history and physical examination. On a physical exam, the ulcers look very distinct and individuals are typically well-appearing and afebrile. If fever is present or if other body systems, such as the eyes or genitalia are involved, other diagnoses, such as Behcet disease  or MAGIC syndrome (i.e., mouth and genital ulcers with inflamed cartilage), may be the underlying cause. During the physical examination, the clinician should also assess for signs of dehydration, especially in infants and children, as the sores are painful and may make eating and drinking difficult. 

Laboratory testing to confirm aphthous stomatitis is usually unnecessary, although diagnostic testing might be considered if the case is persistent or severe. A clinician may order a complete blood count to assess for anemia, as well as iron, folate, or vitamin B12 studies to assess for a nutritional deficiency. Neutropenia, a low white blood cell count, can point to immunocompromise as a cause of canker sores. A serum anti-endomysium antibody and transglutaminase assay can detect celiac disease. Lastly, HIV testing can be considered in cases that are severe, demonstrate persistent herpetiform or major aphthous stomatitis, or if the sores involve keratinized mucosa (i.e., the hard palate and outer lips). 

How is aphthous stomatitis treated?

Aphthous stomatitis can be treated by practicing proper oral hygiene, increasing fluid intake, and using mouth rinses to ease the pain. It is also suggested that the person aims to avoid trauma to the oral mucosa (e.g., biting the cheeks and lips) and avoid spicy, salty, or acidic foods, which may cause further mouth irritation. Dietary supplementation with iron; zinc; or vitamins B1, B2, B6, B12, or C may be useful in individuals with nutritional deficiencies. A gluten-free diet is important for those individuals diagnosed with celiac disease.

For symptom relief of minor cases and to shorten the duration of the sores, one can take acetaminophen or use over the counter topical benzocaine (e.g., Orabase and Anbesol). If the symptoms are more significant, one may be prescribed coating or occlusive agents (e.g., bismuth subsalicylate); antiseptics (e.g., chlorhexidine gluconate and hydrogen peroxide); anti-inflammatory agents, such as glucocorticosteroids (e.g., fluocinonide gel and triamcinolone paste); or immunomodulatory agents (e.g., dapsone, methotrexate, or retinoids). Other treatment options are a one-time local steroid injection, such as triamcinolone; cautery; biopsy of the sore; or laser therapy.

What are the most important facts to know about aphthous stomatitis?

Aphthous stomatitis is also referred to as canker sores and occurs in about 20% of the population. They typically form on non-keratinized mucous membranes lining the inner surfaces of the oral cavity, such as the inner lips, the inside of the cheeks, and the tongue. Aphthous stomatitis can be related to a weakened immune system, eating certain foods, having increased levels of stress, and nutritional deficiencies. Canker sores often recur, and prevention involves managing stress, maintaining a healthy diet, and practicing good oral hygiene. Diagnosis is based primarily on the physical exam, with diagnostic testing used in severe, non-remitting cases. Treatment involves modifying life-style factors that can predispose the individual to developing canker sores as well as using over-the-counter and prescription medications to manage the symptoms. 

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Related links

Aphthous ulcers
Anatomy of the oral cavity
Childhood oral health: Information for patients and families (The Primary School)
The oral microbiota and systemic health
Nasal, oral and pharyngeal diseases: Pathology review

Resources for research and reference

Mayo Foundation for Medical Education and Research. (2018, April 3). Canker sore. In Mayo Clinic. Retrieved September 21, 2021, from,make%20eating%20and%20talking%20difficult. 

Plewa, M.C., & Chatterjee, K. (2021, August 9). Aphthous Stomatitis. In StatPearls [Internet]. Retrieved from

The Children's Hospital of Philadelphia. (2014, August 24). Aphthous stomatitis. In Children's Hospital of Philadelphia. Retrieved September 21, 2021, from