What is Mouth ulcers
A mouth ulcer is an open sore inside the oral cavity. Two common mouth ulcer types are aphthous ulcers (canker sores) and cold sores (caused by the herpes simplex virus).

The types of oral ulcers are diverse, with a multitude of associated causes including: physical or chemical trauma, infection from microorganisms or viruses, medical conditions or medications, cancerous and sometimes nonspecific processes. Once formed, the ulcer may be maintained by inflammation and/or secondary infection.

Symptoms
The symptoms preceding the ulcer may vary according to the cause of the ulcerative process.

Some oral ulcers may begin with a sharp stinging or burning sensation at the site of the future mouth ulcer. In a few days, they often progress to form a red spot or bump, followed by an open ulcer. Sometimes this takes a little bit longer, depending on the cause of the ulcer.

The oral ulcer appears as a white or yellow oval with an inflamed red border. Sometimes a white circle or halo around the lesion can be observed. The grey, white, or yellow coloured area within the red boundary is due to the formation of layers of fibrin, a protein involved in the clotting of blood. The ulcer, which itself is often extremely painful, especially when agitated, may be accompanied by a painful swelling of the lymph nodes below the jaw, which can be mistaken for toothache.

Causes
There are many processes which can lead to ulceration of the oral tissues. In some cases they are caused by an overreaction by the body's own immune system.

Factors that appear to provoke mouth ulcers include stress, fatigue, illness, injury from accidental biting, hormonal changes, menstruation, sudden weight loss, food allergies and deficiencies in vitamin B12, iron and folic acid.

Treatment
Treatments based on antibiotics and steroids are reserved for severe cases, and should be used only under medical supervision.

Some doctors may also prescribe a local anaesthetic, such as lidocaine, for cases of multiple or severe oral ulcers.

Some people benefit from using the over-the-counter topical gel Bonjela, which contains choline salicylate -- choline salicylate is a local analgesic that helps to reduce the pain and inflammation associated with oral ulcers.