Recurring mouth ulcers are caused by several types of microorganisms. In general, the appearance of the mouth ulcer gives the clue to the cause. Aphthous stomatitis is the most common. Often known as “canker sores,” these lesions are shallow, flat, painful erosions that can occur anywhere in the oral cavity. The definite cause of mouth ulcers is unknown but, after several days, the ulcers become covered by a whitish opaque material that contains bacteria.
Curing mouth ulcers consists of topical anesthetic creams, cortisone paste or tetracycline mouthwash. You can also treat aphthous stomatitis by lightly burning the ulcers with a stick tipped with silver nitrate. These lesions tend to recur, however, and may be precipitated by stress and local irritation (such as poorly fitting dentures).
Herpes virus infection is also a common cause of mouth ulcers, which begin as a crop of blisters, often called “fever blisters” or “cold sores.” Eventually, the blisters break, leaving denuded, painful lesions that can take many days to heal. These herpes infections are highly contagious. Treatment with the anti-viral drug acyclovir is usually successful.
Other causes of mouth ulcers include drug reactions, oral pemphigus (a serious autoimmune disorder marked by large blisters on the skin) and benign mucosal pemphigoid (a condition less serious than pemphigus).
Citrus fruits do not cause or worsen mouth ulcers, although these fruits are often painful to eat. Vitamin C does not cure mouth ulcers, which heal by themselves anyway.