Mouth ulcers, otherwise known as canker sores or aphthous ulcers, can be extremely painful. They occur on the inside of the lips, cheeks or under the tongue and usually are red with a whitish coating. They're very common but occur most often among teens or young adults in their twenties. Canker sores can be a symptom of gluten intolerance (gluten is the protein in wheat and other grains). To find out if that's the cause in your case, ask your doctor to test you for gluten intolerance, also known as celiac disease. Beyond that, we don't know for sure what causes recurrent canker sores, although I believe it to be an autoimmune disease, with stress as a possible trigger. Another possible cause is physical trauma (such as accidentally biting the inside of your cheeks). Canker sores tend to occur among women during menstruation. Deficiencies of vitamin B-12, zinc, folic acid, and iron have also been proposed as contributing factors, but there's not much scientific evidence to back up these theories.
Most canker sores heal within a week to 10 days their own. Unfortunately, there's no treatment that reliably eliminates them or relieves the pain they cause. Conventional medicine treats severe canker sores with prescription anti-inflammatory ointments such as Aphthasol or Kenalog in Orabase that you apply directly to the sore. I recommend treating them with DGL (deglycyrrhizinated licorice). Buy it in powder form at the health food store and mix it into a paste or solution to swish in your mouth. You can also apply slippery elm powder mixed to a paste with water or suck on slippery elm lozenges, available in both drug and health food stores. Another home remedy is alum, available in the spice sections of supermarkets. Apply some of the powder directly to an ulcer. It will burn for a few minutes and will promote rapid healing. I also recommend trying mind/body medicine, such as hypnosis or guided imagery. Probiotics (products that help replenish the friendly bacteria in the digestive tract) may also be helpful.
You can try to minimize the discomfort of canker sores by avoiding acidic and spicy foods as well as abrasive foods such as nuts, all of which can be irritating. Switching to a toothpaste that does not contain sodium lauryl sulfate (SLS), a foaming agent, may help reduce recurrences.
Andrew Weil, M.D.