Everything You Need to Know About Mouth Ulcers

Mouth ulcers are common and occur in 20% of the population at least once in their lifetime. They are sore-like lesions inside the oral cavity and can cause difficulty eating and talking. Mouth ulcers are often self-healing; however, persistent, recurring, and large ulcers may need professional attention. Read on to learn about their causes, symptoms, and ways to manage them.

Key takeaways:

Mouth ulcers, often known as canker sores, are painful sores that occur within the mouth, commonly on the tongue, the inner surface of lips, and the inside of the cheeks. Ulcers usually occur due to a break or discontinuity in the inner mucosal lining of the oral cavity.


Oral ulcers are white-yellow with irregular reddish edges. They can appear one at a time or multiple together. Mouth ulcers are not contagious but may grow in size, spread to other sites in the mouth, and recur frequently. While the exact reasons for mouth ulcers can vary, some diseases, triggers, and risk factors can aggravate the process.

What causes ulcers in the mouth?

Ulcers in the mouth are often due to local triggers that irritate the oral lining. These include:

  • Accidental bites. Sharp teeth edges can cause you to bite while chewing or talking.
  • Trauma or injury. Ill-fitting dentures, a wire from an orthodontic brace, or a high point in a dental filling can irritate the mouth and cause ulcers.
  • Brush bristles and toothpaste ingredients. Some ingredients (mainly sodium lauryl sulfate) can irritate the oral soft tissues.
  • Food. Food that is too hot, acidic, or spicy foods can be a source of constant irritation.

Besides these local triggers, mouth ulcers are also linked to nutritional deficiencies, stress, and systemic diseases, such as:

  • Anemia. Low levels of iron, vitamin B12, or folic acid can cause oral ulcers.
  • High stress and anxiety. A type of recurring aphthous ulcer, common among females, has been linked to increased stress and anxiety levels. Changes in hormone levels are another factor behind relapsing oral ulcers.
  • Systemic diseases. Oral lichen planus (a condition that develops a white, lacy pattern within the cheeks), celiac disease and Crohn's disease (conditions that affect the digestive system), and HIV or lupus (characterized by a weak and altered immune response) can manifest as mouth ulcers.
  • Genetics. Mouth ulcers can run in families. Research shows that 40% of people with oral ulcers have a positive history in the family.
  • Viral infections. Chickenpox and hand, foot, and mouth disease are viral infections that can cause mouth ulcers. The Herpes virus causes cold sores, which are distinct from mouth ulcers. Cold sores affect the areas around the lips (commonly the lip corners) and can follow an initial episode of fever, weakness, and tingling sensations around the affected areas.

Studies highlight that aphthous-like oral ulcers can be noted among SARS-CoV-2 patients. These are commonly noted on the tongue due to the high expression of angiotensin-converting enzyme 2 (ACE2) receptor cells in the tongue epithelial cells. ACE2 are the target host cell receptors for the COVID-19 virus.


What are the symptoms of mouth ulcers?

Mouth ulcers are usually harmless, but they can be a source of constant discomfort and unease. These ulcers appear in the tongue, lips, and cheek mucosa. Oral ulcers are painful. The pain can vary from mild to intense, depending on the severity of the ulcers. The pain often worsens as you eat, talk, and chew. Mouth ulcers have a typical appearance. They are whitish at the center and surrounded by a red and inflamed border. These can vary in size, shape, and number.

A dentist is the right person to diagnose a mouth ulcer. Oral pathologists diagnose an oral ulcer from its appearance and patient history. Your dentist might advise on a few tests or a biopsy if they suspect a disease associated with the ulcers.

What are the types of oral ulcers?

Mouth ulcers can be minor, major, or herpetiform, depending on the condition's size, number, and severity.

Minor oral ulcers are small and measure less than 5 mm. These usually heal in 10–14 days and leave no scar behind. Major oral ulcers are more prominent and measure around 10 mm or more. These can take some time to heal and leave behind scars. Herpetiform sores appear similar to the cold sores caused by the Herpes virus but are not related. They occur as tiny clusters of reddish bumps on the tongue and self-heal.

How to treat a mouth ulcer

Commonly, mouth ulcers heal in 1014 days without treatment. Any treatment, if advised, aims to reduce discomfort and pain while speeding up the healing process. If you suffer from mouth ulcers, here are some self-care tips that might work:

  • Avoid triggers. Be it a spicy food, a toothpaste that irritates, or a stiff brush bristle.
  • Use an anesthetic/ antiseptic topical ointment. A dentist can guide you on which best suits you. If you decide to visit a dentist, they may prescribe you an antimicrobial mouthwash (chlorhexidine 0.2% aqueous mouthwash) and painkillers. When needed, a corticosteroid may be advised to speed the healing.
  • Consult a dentist. If an oral ulcer lasts more than three weeks, it might be a sign of a serious condition.

Ways to prevent mouth ulcers


Mouth ulcers can affect you out of the blue. Certain precautions can reduce your chances of getting a mouth ulcer.

  • Maintain oral hygiene. Brush and floss regularly.
  • Decrease anxiety and stress. Sufficient sleep and exercise can reduce the stress hormones in the body.
  • Avoid irritating foods. Any spicy foods, acidic drinks, or toothpaste that aggravates an existing oral ulcer should be avoided.
  • Eat a balanced diet. Having a well-balanced diet is the best way to overcome any nutritional deficiency.
  • Visit your dentist regularly. A dentist will diagnose the cause of the ulcers and might recommend smoothing out the sharp edges of a tooth, covering up the wire edges from a brace, or correcting a misfit denture, as needed.

When to see a dentist

Mouth ulcers usually resolve within two weeks. You should consult a dentist if it persists for more than three weeks. If the ulcer is painless and new ones keep appearing, it's best to consult your dentist. Large, excruciating sores that compromise your daily activities need professional help. Persistent oral ulcers can be a sign of oral cancer. It's best to consult a dentist to rule out the risk.


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