Also known as canker sores, mouth ulcers are painful lesions that develop on the soft tissues of your mouth or at the base of your gums. Unlike cold sores, mouth ulcers are not contagious.

Mouth ulcers are painful round or oval sores in the mouth often on the inside of the cheeks or lips.

Mouth ulcers (aphthous ulcers) are very common in women and young adults and are harmless. These oval or round white sores usually appear at the most inconvenient times and are very painful especially when eating, drinking, or brushing your teeth.


They are usually white but can be red, yellow, or grey in colour and are mostly inflamed around the edges. Most mouth ulcers appear on the inside of the lips or cheeks, the floor of the mouth, or under the surface of the tongue. Most mouth ulcers heal within 10-14 days, although they may be painful for several weeks in more severe cases. 


There are three main types of mouth ulcers:

  • Minor ulcers are the most common. They are small and usually heal naturally.
  • Major ulcers are deeper and larger than minor ulcers and have a raised or irregular border. They take several weeks to heal and can cause scarring.

Herpetiform ulcers form as multiple (between 5 and 100) pinhead-sized sores. They often fuse together to form larger, irregular shaped sores, which are very painful.


In most cases, mouth ulcers are not caused by an infection and therefore cannot be passed from person to person through kissing, or by sharing drinks and utensils. Most minor, single mouth ulcers are caused by damage to the mouth. This can occur by accidentally biting the inside of the cheek while eating.

Mouth damage can also occur from using a toothbrush incorrectly or from a sharp tooth or filling or dental appliances, such as braces or ill-fitting dentures. The cause of recurrent mouth ulcers is often unknown, but several factors may increase the chances of getting recurrent ulcers:

  • Stress and anxiety
  • Oral trauma
  • Excessive tooth brushing
  • Chewing sharp or hard foods
  • Hormonal changes
  • Eating certain foods
  • Smoking


Recurrent mouth ulcers may be caused by an underlying medical condition. • Vitamin B12 deficiency: Vitamin B12 helps to produce red blood cells and keeps the body’s nervous system healthy. A lack of vitamin B12 can cause tiredness, shortness of breath, and mouth ulcers.

  • Iron deficiency: If the diet is lacking in iron, the red blood cells will not be able to carry adequate oxygen. Sometimes, an iron deficiency can also cause mouth ulcers.
  • Coeliac disease: This disease is caused by intolerance to a protein called gluten, found in wheat, rye, and barley. The condition causes the small intestine to become inflamed. Mouth ulcers are also a common symptom in adults with coeliac disease.
  • Crohn’s disease: It is a condition that causes inflammation of the gut, leading to ulcers developing in both the stomach and mouth.
  • Immunodeficiency: Any condition that attacks or suppresses the body’s immune system (e.g. HIV) can cause mouth ulcers.
  • Medication: Occasionally, mouth ulcers are caused by a reaction to a medicine, but this is usually a temporary effect.


Symptoms vary and depend on the specific cause of the mouth ulcer. Symptoms may include open sores in the mouth, on the tongue, soft palate, or inside the cheeks that causes pain or discomfort. Sometimes a tingling or burning sensation prior to the appearance of the sores is noted.


Most mouth ulcers do not require specific treatment. They will usually heal naturally without the need for treatment if they are infrequent, mild, and do not interfere with the daily activities, such as eating. The goal of treatment is to relieve symptoms. Gentle, thorough oral hygiene may relieve some of the symptoms.

The cause, if known, should be treated. Topical antihistamines, antacids, corticosteroids, or other soothing preparations may be recommended for applying directly to the ulcer.

  • Antimicrobial mouthwashes such as chlorhexidine gluconate or povidone iodine help to kill any micro-organisms, such as bacteria, viruses, or fungi that may cause a mouth infection.
  • Mouth ulcer medications containing a low dose of corticosteroids are usually enough to lower the level of inflammation. Reducing the inflammation of the ulcer will make less painful.
  • If the mouth ulcer is very painful, a painkiller can be applied directly to the ulcer. Benzydamine which can either be taken as a mouthwash or a spray can be very effective. A local anaesthetic such as benzocaine, combined with chlorhexidine can provide both analgesic and antimicrobial effects.
  • Some products form a protective barrier over mouth ulcers and oral lesions, giving safe, effective, and speedy relief.

They can be used by both adults and children and are available in the form of a soothing gel, convenient spray, or mouth wash. The soothing action relieves the pain of mouth ulcers within minutes and lasts for up to six hours.


When a mouth ulcer lasts longer than three weeks, keeps coming back, or becomes more painful and red – this may be a sign of an infection. Although most mouth ulcers are harmless, a long-lasting mouth ulcer is sometimes a sign of mouth cancer and it’s best to get it checked.