Aphthous ulcers are canker sores. These small round or oval ulcers can develop on the mucous membranes of the mouth or genitals. They usually form on the soft pinkish-red tissue inside the mouth that is not directly attached to bone. For example, they can form inside the lips and cheeks and underneath the tongue. They do not usually form on the roof of the mouth (hard palate) or on the gums.

While aphthous ulcers are not life-threatening, they can be very painful. The pain can last up to 10 days and the ulcer usually heals within one to three weeks. Large aphthous ulcers, measuring greater than 1 centimeter in diameter, can take longer to heal.

Aphthous ulcers are not an AIDS-defining illness. In other words, if you have HIV and experience an aphthous ulcer, this does not mean that you have AIDS. However, aphthous ulcers are more common in HIV-positive people and are more likely to recur in HIV-positive people. Aphthous ulcers are also commonly present in other medical conditions, including Crohn’s disease and inflammatory bowel disease (IBD).

Even though aphthous ulcers are very common among HIV-positive and HIV-negative people, it’s still not clear why they happen. It’s likely that hyperactivity of the immune system has something to do with aphthous ulcers, but it’s not known how this happens.

People with a history of aphthous ulcers in their family are more likely to get aphthous ulcers. Aphthous ulcers can also be caused by emotional stress and lack of sleep. If you bite the inside of your cheek, this can also result in an aphthous ulcer. People with nutritional problems, such as vitamin B, iron, and folic acid deficiency, are also more likely to develop aphthous ulcers. Some women report aphthous ulcers at certain times in their menstrual cycles. Aphthous ulcers are also a side effect of Hivid (ddC), an anti-HIV medication.

What are the symptoms and how are they diagnosed?

Aphthous ulcers usually begin as a burning or tingling sensation. A red spot or bump usually forms, which develops into an open ulcer. The ulcers are usually small, less than 1 centimeter in diameter, but larger ulcers are possible. A single ulcer can form, but so can a cluster of ulcers at the same site.

Aphthous ulcers are usually painful and can make eating and drinking certain foods/beverages difficult.

Once the aphthous ulcer begins to heal, a whitish-gray membrane will form over the ulcer. Large aphthous ulcers may cause some scarring upon healing.

Diagnosing aphthous ulcers can be difficult, given that they can resemble viral infections that cause similar ulcers, such as herpes simplex virus (HSV). However, aphthous ulcers are not usually responsive to therapies used to treat HSV, so a correct diagnosis might not be made until after viral infections like HSV have been ruled out.

It is not usually necessary to biopsy aphthous ulcers. However, if the ulcers are large, it might be necessary to conduct a biopsy to rule out more serious problems, such as cancer.

How are they treated?

Corticosteroid creams and gels are the most commonly used treatments for aphthous ulcers. These topical treatments calm the activity of the immune system, which is believed to be responsible for the ulcers, at the site where the aphthous ulcer has developed. The most effective topical corticosteroids are betamethasone (Alphatrex, Diprolene, Maxivate), fluocinonide (Lidex), fluocinolone (Synalar, Fluonid), clobetasol (Temovate), hydrocortisone (Cortaid, Westcort), and triamcinolone (Aristocort, Flutex, Kenalog). These topical treatments should be used carefully, as many of them (except hydrocortisone and triamcinolone) can cause the adrenal glands (located on top of the kidneys) to slow production of adrenalin, an important hormone. Prolonged use of these treatments can also increase the risk of certain oral infections, like candidiasis.

Large aphthous ulcers, or ulcers that do not respond to topical corticosteroids, are often treated using more powerful corticosteroids taken in pill form, such as prednisone.

Thalidomide (Thalomid) has been shown to be a very effective treatment for aphthous ulcers. However, it is only approved in the United States for the treatment of leprosy. While it is possible to fill a prescription for thalidomide to treat aphthous ulcers, the drug must not be used by women who are pregnant. Thalidomide can cause severe birth defects.

Can they be prevented?

Not really, given that it’s not clear who is at greatest risk for aphthous ulcers. They can occur in HIV-positive people with both healthy and suppressed immune systems, so it is not clear if anti-HIV drug therapy helps to reduce the risk (or enhance the treatment) of aphthous ulcers.

For people who experience frequent recurrences of aphthous ulcers, prolonged corticosteroid therapy may be necessary.

Are there any experimental treatments?

If you would like to find out if you are eligible for any clinical trials that include new therapies for the treatment or prevention of aphthous ulcers, visit ClinicalTrials.gov, a site run by the U.S. National Institutes of Health. The site has information about all HIV-related clinical studies in the United States. For more info, you can call their toll-free number at 1-800-HIV-0440 (1-800-448-0440) or email contactus@aidsinfo.nih.gov.

Last Reviewed: January 18, 2016