By: David D. Rolf II, D.M.D., M.Sc.
Director of Education Dental1.org

Clinical Overview

Better known as a “canker sore”, an aphthous ulcer (pronounced “ap-thus”) can be a relatively minor looking but very painful oral sore. Because aphthous ulcer sufferers usually experience ulcers that will come back in different places in the mouth over and over again throughout their lifetime, aphthous ulcers are also referred to as recurrent aphthous ulcers (RAU) or recurrent aphthous stomatitis (RAS). Aphthous ulcers are the most common type of mouth sore, affecting about 20 percent of the general population.

The majority of healthcare information available to the public about aphthous ulcers often mentions that little effective treatment is available – that people with aphthous ulcers have to suffer with the problem for 1-2 weeks until the ulcer heals on its own. In fact, most aphthous ulcers can be treated at home with prescription medications that can significantly reduce the pain and help the ulcer heal more quickly.

Aphthous ulcers are a benign, non-harmful oral lesion (the term “lesion” refers to an area or site of tissue damage). They are not contagious and so can’t be spread to another person from oral contact, or from touching another person, or “caught” if someone sneezes. Aphthous ulcers should not be confused with cold sores, also known as fever blisters, which is another common but highly contagious oral ulcer caused by the herpes simplex virus HSV-1. Cold sores most often occur on the outside of the lip or mouth, while aphthous ulcers only occur inside the mouth.

Aphthous ulcers can occur with one or more sores in the mouth at a given time. The ulcers occur only on the mucosal tissue on the inside of the mouth, found in the following areas: The inside lining of the lips and cheeks; the underside and sides of the tongue; the tissue underneath the tongue (called the floor of the mouth); and the back of the throat. Minor aphthous ulcers make up about 80 percent of all cases and are generally small in size (1/8 inch to 1/4 inch in diameter, or two to five mm), but are painful and easily irritated by eating and speaking. Major aphthous ulcers are often twice as large as minor ulcers (more than 1/2 inch, or greater than 10mm in diameter) and make up only about 10 to 15 percent of cases. Major aphthous ulcers can be more debilitating due to the increased pain and longer healing time involved.

Aphthous ulcers often begin as a small red bump or pimple in the mouth, and the bump may feel like it is burning, tingling or sore. This is the earliest, or prodromal, stage of an aphthous ulcer and is the best time to treat the ulcer. The bump quickly breaks down into a round, shallow, slightly raised ulcer that looks yellow-gray in the middle and is surrounded by a red halo of inflammation. The ulcer remains like this until it heals, usually in 7 to 10 days for an untreated minor ulcer and longer (weeks or more) for a major ulcer. Healing times are generally shorter for patients who receive treatment from their dentist, using prescription corticosteroid medications.

The exact cause of aphthous ulcers is not known, but research studies suggest that aphthous ulcers are caused by changes in immune system function in otherwise healthy individuals.

The most common reasons why aphthous ulcers appear in the mouth are:

1. Trauma, such as biting the inside of the cheek or lip, or having a sharp piece of food cut or scrape the inside lining of the mouth (called the mucosa).

2. Irritation of the oral tissues by orthodontic braces, a rough or sharp edge of a tooth, filling or denture.

3. Stress

4. Food and/or food allergies, such as chocolate, wheat flour products containing gluten, peanuts, almonds, cheese, strawberries, tomatoes or coffee.

5. Toothpastes and/or mouthwash that contain a foaming (detergent) chemical called sodium laurel sulfate (SLS).

6. Hormonal changes, including the menstrual cycle.

There is also family history, or hereditary/genetic component associated with aphthous ulcers: More than one family member may suffer from aphthous ulcers and the tendency to develop aphthous ulcers can be passed on to future generations. Aphthous ulcers can appear at any age, but usually occur for the first time in childhood or adolescence.

Certain diseases and conditions can also produce recurring oral ulcers, such as: nutritional deficiencies of B vitamins and/or folic acid; gastrointestinal disorders such as celiac disease (gluten sensitivity) and Crohn’s disease; Behcet’s syndrome; PFAPA syndrome (periodic fever, aphthae, pharyngitis and adenitis which is sometimes seen in young children); and in immune system deficiencies such as HIV. When a patient has aphthous ulcers that do not appear to respond well to standard treatments, or the patient also has other systemic symptoms in addition to the aphthous ulcers, a dentist specializing in oral medicine and a physician may need to be consulted to properly diagnose and treat these other conditions.

Last updated: Aug-29-06