A canker sore, also known as an aphthous ulcer, is a common and often painful lesion that can develop inside the mouth, including on the inner cheeks. These small, shallow ulcers can make eating, drinking, and talking uncomfortable. While generally harmless and not contagious, understanding their characteristics and causes helps manage their occurrence and discomfort.
What Canker Sores Are
Canker sores typically present as small, round or oval-shaped ulcers with a white or yellowish center and a distinct red border. They commonly form on soft tissues within the mouth, such as the inner cheeks, lips, tongue, or at the base of the gums. Unlike cold sores, canker sores are not caused by a virus and cannot be spread through contact.
Most are minor aphthous ulcers, usually less than 1 centimeter across and healing within one to two weeks without scarring. Some individuals may experience major canker sores, which are larger, deeper, and can take several weeks to heal, potentially leaving scars. Herpetiform canker sores, though not caused by the herpes virus, appear as clusters of tiny ulcers that may merge into a larger sore.
Common Causes
The exact cause of canker sores is often unclear, but several factors are associated with their development. Minor injuries to the mouth, such as accidentally biting the cheek, dental work, or aggressive brushing, can trigger these sores. Certain foods, particularly acidic items like citrus fruits, tomatoes, or spicy foods, as well as those with abrasive textures, can also be triggers.
Emotional stress can weaken the immune system, increasing susceptibility to canker sores. Nutritional deficiencies, specifically in vitamin B12, folate (folic acid), iron, and zinc, have been linked to recurrent canker sores. Hormonal shifts, such as those during menstruation, can also play a role.
Certain oral hygiene product ingredients, like sodium lauryl sulfate (SLS) in toothpastes, can irritate oral tissues and contribute to canker sore development. Some medical conditions, including celiac disease, inflammatory bowel diseases like Crohn’s, and a compromised immune system, can also increase the likelihood of canker sores.
Relief and Treatment Options
A variety of approaches can help alleviate pain and promote healing of canker sores. Rinsing the mouth with saltwater (one teaspoon salt in half a cup warm water) or a baking soda solution (one teaspoon baking soda in half a cup warm water) can reduce discomfort and keep the area clean. Applying milk of magnesia directly to the sore a few times daily may offer relief by neutralizing acid and coating the ulcer.
Over-the-counter topical gels, creams, or pastes containing ingredients like benzocaine or lidocaine can numb the affected area and provide temporary pain relief. Oral rinses designed for canker sores, including those with hydrogen peroxide or chlorhexidine, can help prevent infection and inflammation. Honey or aloe vera gel may also aid healing.
Avoiding irritating foods, such as acidic, spicy, or crunchy items, is advisable during healing. For persistent or particularly painful sores, a healthcare provider might prescribe stronger mouth rinses containing corticosteroids like dexamethasone, or topical steroid ointments to reduce inflammation and pain. Pain relievers like ibuprofen or acetaminophen can also help manage discomfort.
Prevention and When to Seek Medical Advice
Preventing canker sores often involves identifying and avoiding personal triggers. Maintaining good oral hygiene, including gentle brushing with a soft-bristled toothbrush and flossing regularly, can help prevent minor injuries and keep the mouth clean. Switching to toothpastes free of sodium lauryl sulfate (SLS) may reduce outbreak frequency for some.
Eating a balanced diet rich in fruits, vegetables, and whole grains can help ensure adequate intake of essential vitamins and minerals, such as vitamin B12, folate, iron, and zinc, which are important for oral health. Managing stress through relaxation techniques can also be beneficial, as stress is a common trigger. If dental appliances like braces cause irritation, using orthodontic wax can protect soft tissues.
While most canker sores heal on their own within two weeks, medical advice should be sought in certain instances. Consult a doctor or dentist if a canker sore is unusually large, causes extreme pain, or persists for more than two weeks. Other reasons to seek professional evaluation include frequent recurrence, new sores appearing before old ones heal, or sores accompanied by high fever, difficulty eating or drinking, or a rash.