Aphthous Stomatitis · What Is It, Symptoms, and More

Aphthous stomatitis, also known as a canker sore, refers to small, painful ulcers that appear on the inside of the mouth. They typically only form on non-keratinized areas of the oral mucosa, such as the inside of the lips, cheeks, or soft palate, the floor of the mouth, gums or tongue. Aphthous ulcers are very similar to ulcerations caused by herpes simplex virus (HSV), also known as cold sores, but these tend to affect the keratinized mucosal surfaces, such as the outer surfaces of the lips. Unlike cold sores, canker sores are non-contagious and idiopathic, meaning it is not clear why some individuals get aphthous ulcers and others don’t.  

Aphthous stomatitis affects up to 20% of the population and is more common in individuals assigned female at birth. They tend to occur most often in young individuals between 20 and 30 years old and become less common with advancing age. 

The exact cause of aphthous stomatitis is not currently known; however, there are many factors that are thought to contribute. Associated risk factors include a weakened immune system, stress and anxiety, and physical injuries inside the mouth, like from biting the lip, badly fitting dentures, or overzealous tooth-brushing. Certain acidic or spicy foods, such as coffee, chocolate, cheese, nuts, and citrus fruits may also trigger or worsen aphthous ulcers in some individuals. Likewise, sensitivity to ingredients in toothpaste and oral hygiene products, like sodium lauryl sulfate, may also trigger a canker sore. Other suspected causes include hormonal changes 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. Finally, certain medications, especially chemotherapeutic agents, may also cause canker sores as a side effect.  

Although less commonly, canker sores may occur as a result of medical conditions, such as celiac disease, which is a gastrointestinal disorder caused by an autoimmune intolerance to gluten, a protein found in most grains. They can also occur as a result of inflammatory bowel diseases, such as Crohn disease and ulcerative colitis. Lastly, Behcet disease, a rare disorder that causes inflammation throughout the body, can predispose an individual to canker sores.  

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 foods that irritate the mouth and 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.  

Often, those with recurrent canker sores have a family history of the disorder, which may be due to genetic factors or to a shared factor in the environment, such as certain foods. 

Initial signs and symptoms of aphthous stomatitis include a burning sensation or discomfort in the oral mucosa starting a day or two before the onset of ulcerations. Most cases consist of minor aphthous ulcerations that begin as a small, raised bump on the inside of the mouth. As it heals, the bump turns into an ulcer covered by a fibrous membrane cap that looks yellowish or white and has well-defined margins. Minor aphthous ulcers are usually minimally painful, with individual lesions measuring a few millimeters (mm) and healing within 7 to 10 days without scarring. Unlike common sores caused by viral infections, infectious symptoms such as fever, rash, headache, or enlarged lymph nodes are typically absent.  

There are also two other unusual variations of aphthous stomatitis called major aphthous ulcers and herpetiform ulcers, which are much more severe and debilitating. Major aphthous ulcers are deeper, larger (i.e., often 2 to 3 cm in diameter), can have irregular raised borders, and typically take many weeks or months to heal, often leaving a scar.  

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 millimeters (mm) in diameter. They can sometimes coalesce to form large, ulcerated patches in the mouth. Although they usually heal in a few days, new ulcers can recur so frequently that they cause continuous pain and difficulty with eating and drinking. 

Aphthous stomatitis is usually diagnosed based on a complete history and physical examination. On a physical exam, aphthous 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 suspected. During the physical examination, clinicians should assess for signs of dehydration, especially in infants and children, as the sores can be very painful and may make eating and drinking difficult.  

Laboratory testing to confirm aphthous stomatitis is usually not necessary, although diagnostic testing might be considered if the case is persistent or severe. Diagnostic tests may include 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., hard palate and outer lips).  

There is no cure for aphthous stomatitis, so the main goal is to identify and avoid triggers. Preventive measures include avoiding trauma to the oral mucosa, using well-fitting dentures, and brushing the teeth with a soft toothbrush. In cases of nutritional deficiencies, dietary supplementation with iron, zinc, or vitamin B may be recommended. Following a gluten-free diet is important for individuals diagnosed with celiac disease, both to prevent aphthous ulcers and gastrointestinal symptoms. 

For symptom relief and to shorten the duration of the sores, individuals can take acetaminophen or use over-the-counter topical benzocaine. If the symptoms are more severe, treatment may include coating or occlusive agents (e.g., bismuth subsalicylate), antiseptics (e.g., chlorhexidine gluconate and hydrogen peroxide), anti-inflammatory agents, such as corticosteroids (e.g., fluocinonide gel and triamcinolone paste) or immunomodulatory agents (e.g., dapsone, methotrexate, or retinoids). Finally, other treatment options for severe cases include cauterization or laser therapy.