A mouth ulcer is a break in the lining of the mouth that uncovers the sensitive tissue beneath. All mouth ulcers look very much the same, but they vary considerably in cause and seriousness.

The two most common and painful types of ulcers are apthous ulcers, which tend to occur when you are under stress, feeling run-down or ill, and traumatic ulcers, which result from an injury to the lining of your mouth. A toothbrush, a rough denture, or hot food may cause such an injury. Some mouth ulcers are caused by viral infection.

A virus that commonly causes mouth ulcers is the herpes simplex. This virus causes blisters, which eventually turn into ulcers. Rarely, an ulcer may be the first sign of a tumor of the mouth, or a more generalized disease such as leukemia or anemia. Mouth ulcers are extremely common. Apthous ulcers occur most often in adolescents and young adults, and more often in women (especially just before a menstrual period).

Oral Signs and Symptoms :

You usually first become aware of an ulcer when you eat something spicy or acidic that makes it sting. All ulcers look much the same. You can usually see them in the mirror as pale yellow spots with red borders.

Apthous ulcers are small measuring 2 to 3mm (1/10th inch) across. They usually appear in clusters on the sides of the tongue or gums and last for 3 to 4 days. A traumatic ulcer is usually larger and lasts for a week or more. When a traumatic ulcer is caused by a rough tooth or denture, it will not heal until the cause of the irritation is removed.

Treatment :

The vast majorities of mouth ulcers do not indicate any major health problem and usually heal by themselves. But if an ulcer fails to heal within 2 weeks or if ulcers keep recurring, then see your physician or dentist to find out if the ulcers are being caused by a more serious underlying condition. Your physician may want you to have blood test taken and you may also have to undergo a biopsy of the ulcer. In this procedure part of the ulcer is removed under a local anesthetic, so that it can be examined. The results of these tests will show whether the ulcer signifies a serious disorder, which will then be dealt with as necessary.

Self-help :

You can buy various nonprescription topical applications and lozenges that numb and protect the exposed tissue in an ulcer. These preparations relieve the pain and may help the ulcer to heal. Take vitamin B and C supplements if you are run down, especially for women and students who get mouth ulcers often. 
Antiseptic mouthwashes or rinsing your mouth with warm salt-water may also help.

To minimize discomfort avoid eating spices (such as chili and pepper) or acidic foods (grapefruits and oranges, for example). Drink lots of water to avoid a dry mouth. Eat a healthy well-balanced diet or fruit and green vegetables.  The ulcer will also be sensitive to hot foods or drinks.

Professional help :

To deal with persistent apthous ulcers, your physician may prescribe a mouth rinse or a cream containing a steroid drug