Aphthous ulcers are small round or oval ulcers that develop on the soft tissue inside the mouth. They can form inside the lips and cheeks, on or under the tongue and at the base of the gums. They do not usually form on the roof of the mouth or tissue connected to bone. Anyone can get them.

Aphthous ulcers can be very painful though they’re not life-threatening. Most ulcers heal within a couple weeks, while larger ones may take up to 6 weeks to fully heal. Aphthous ulcers are also not an AIDS-defining illness, but they are more common and more likely to recur in people with HIV. They can also appear with other medical conditions, such as Helicobacter pylori infection, Crohn’s disease and inflammatory bowel disease.

It’s still not clear why aphthous ulcers happen. It may be due to a trigger that causes the immune system to become hyperactive. They can make eating and drinking certain foods and beverages difficult or impossible. If this is the case or if the pain is too much to manage on your own, seek your doctor’s help.

People with a family history of aphthous ulcers are more likely to get them. Emotional stress, dental work, biting your cheek, brushing too hard, and lack of sleep may trigger them. Further, people who don’t get enough vitamin B, iron, zinc, and folic acid are also more at risk. Spicy, acidic and other foods may be triggers as well as hormonal shifts during menstruation. Lastly, toothpastes and mouth washes with sodium lauryl sulfate may cause them.


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 that turns white or yellow. The ulcers are usually small, from .25 to .50 inch in diameter, but larger ulcers are possible. A single ulcer usually forms, but clusters can also occur. Once they begin to heal, a whitish-gray membrane forms over the ulcer. Large aphthous ulcers may cause some scarring after healing.

Your doctor or dentist can diagnose aphthous ulcers by looking at them. Other tests are not needed, unless the ulcers suggest other conditions are present. Another common oral condition, cold sores (herpes), tend to look different and usually appear outside the mouth on the lips. However, both can occur together, so it’s helpful to be diagnosed and treated properly. Aphthous ulcers are not cancerous, but if you’re concerned the sore may be cancer, seek medical help.


How are they treated?

Some people just deal with the discomfort if it’s not severe. Beyond that, various steroid products (mouth rinses, pastes, creams, gels and oral medications) are available over-the-counter and by prescription. These can reduce inflammation and pain until the ulcers heal.

Steroid medications include benzocaine, betamethasone, clobetasol, dexamethasone, fluocinonide, fluocinolone, hydrocortisone, hydrogen peroxide, and triamcinolone. Some of these should be used carefully, as prolonged use of them (except hydrocortisone and triamcinolone) can cause the adrenal glands to slow production of adrenalin or 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 a pill form of a stronger corticosteroid, such as prednisone.

While it is possible to fill a prescription for thalidomide (Thalomid) to treat aphthous ulcers (an FDA-approved drug for leprosy), it must not be used by women who are or may be pregnant. Thalidomide can cause severe birth defects.

Can they be prevented?

Aphthous ulcers tend to recur, although these tips may help prevent them:

  • Avoid foods and drinks that trigger the ulcers
  • Maintain a healthful diet, especially foods with folic acid, vitamin B, zinc and iron
  • Maintain good oral hygiene: brush and floss regularly, use products that don’t irritate mouth surfaces
  • Reduce stress


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: October 19, 2018