Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums. Unlike cold sores, canker sores don't occur on the surface of your lips and aren't contagious. They can be painful, however, and can make eating and talking difficult.
Most canker sores go away on their own in a week or two. Check with your doctor or dentist if you have unusually large or painful canker sores or canker sores that don't seem to heal.
Most canker sores are round or oval with a white or yellow center and a red border. They form inside your mouth — on or under your tongue, inside your cheeks or lips, at the base of your gums, or on your soft palate. You might notice a tingling or burning sensation a day or two before the sores actually appear.
There are several types of canker sores, including minor, major and herpetiform sores.
Minor canker sores
These most common canker sores:
Are usually small
Are oval shaped
Heal without scarring in one to two weeks
Major canker sores
These less common sores:
Are larger and deeper than minor canker sores
Have irregular edges
May take up to six weeks to heal and can leave extensive scarring
Herpetiform canker sores
These canker sores, which usually develop later in life:
Are pinpoint size
Often occur in clusters of 10 to 100 sores
Have irregular edges
Heal without scarring in one to two weeks
When to see a doctor
Consult your doctor if you experience:
Unusually large canker sores
Recurring sores, with new ones developing before old ones heal
Persistent sores, lasting three weeks or more
Sores that extend into the lips themselves (vermilion border)
Pain that you can't control with self-care measures
Extreme difficulty eating or drinking
High fever along with canker sores
The precise cause of canker sores remains unclear, though researchers suspect that a combination of several factors contributes to outbreaks, even in the same person.
Possible triggers for canker sores include:
A minor injury to your mouth from dental work, overzealous brushing, sports mishaps, spicy or acidic foods, or an accidental cheek bite
Toothpastes and mouth rinses containing sodium lauryl sulfate
Food sensitivities, particularly to chocolate, coffee, strawberries, eggs, nuts, cheese and highly acidic foods, such as pineapple
A diet lacking in vitamin B-12, zinc, folate (folic acid) or iron
An allergic response to certain bacteria in your mouth
Helicobacter pylori, the same bacteria that cause peptic ulcers
Hormonal shifts during menstruation
Canker sores may also occur because of certain conditions and diseases, such as:
Celiac disease, a serious intestinal disorder caused by a sensitivity to gluten, a protein found in most grains
Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis
Behcet's disease, a rare disorder that causes inflammation throughout the body, including the mouth
A faulty immune system that attacks healthy cells in your mouth instead of pathogens, such as viruses and bacteria
HIV/AIDS, which suppresses the immune system
Unlike cold sores, canker sores are not associated with herpes virus infections.
Treatment & Drugs
Treatment usually isn't necessary for minor canker sores, which tend to clear on their own in a week or two. But large, persistent or unusually painful sores often need medical care. A number of treatment options exist, ranging from mouth rinses and topical ointments to systemic corticosteroids for the most-severe cases.
Mouth rinses. If you have several canker sores, your doctor may prescribe a mouth rinse containing the steroid dexamethasone (dek-suh-METH-uh-sown) to reduce pain and inflammation. Oral suspensions of the antibiotic tetracycline also can reduce pain and cut healing time, but tetracycline has drawbacks. It can make you more susceptible to oral thrush, a fungal infection that causes painful mouth sores, and it can permanently discolor children's teeth.
Topical pastes. Over-the-counter and prescription pastes with active ingredients such as benzocaine (Anbesol), amlexanox (Aphthasol) and fluocinonide (Lidex, Vanos) can help relieve pain and speed healing if applied to individual sores as soon as they appear. Your doctor may recommend applying the paste to the sore two to four times a day until it heals.
Oral medications. Medications not intended specifically for canker sore treatment, such as the heartburn drug cimetidine (Tagamet) and colchicine, which is normally used to treat gout, may be helpful for canker sores. Your doctor may prescribe oral steroid medications when severe canker sores don't respond to other treatments, but because of serious side effects, they're usually considered a last resort.
Cautery of sores. During cautery, an instrument or chemical substance is used to burn, sear or destroy tissue. Debacterol is a topical solution designed to treat canker sores and gum problems. By chemically cauterizing canker sores, this medication may reduce healing time to about a week. Silver nitrate — another option for chemical cautery of canker sores — hasn't been shown to speed healing, but it may help relieve canker sore pain.
Nutritional supplements. Your doctor may prescribe a nutritional supplement if you consume low amounts of important nutrients, such as folate (folic acid), vitamin B-6, vitamin B-12 or zinc.
If your canker sores relate to a more serious health problem, your doctor will treat the underlying condition.
Lifestyle & Home Remedies
To help relieve pain and speed healing:
Rinse your mouth. Use salt water; baking soda (dissolve 1 teaspoon of soda in 1/2 cup warm water); or a mixture of 1 part — such as 1 teaspoon — diphenhydramine (Benadryl) to either 1 part Kaopectate or 1 part Maalox. Be sure to spit out the mixtures after rinsing.
Dab a small amount of milk of magnesia on your canker sore a few times a day.
Cover canker sores with a paste made of baking soda plus a small amount of water — just enough to make a paste.
Try over-the-counter products that contain the numbing agent benzocaine, such as Anbesol and Orajel.
Avoid abrasive, acidic or spicy foods that can cause further irritation and pain.
Apply ice to your canker sores by allowing ice chips to slowly dissolve over the sores.
Brush your teeth gently, using a soft brush and toothpaste without foaming agents.