Treatment is usually not necessary. In most cases, the canker sores go away by themselves.
Severe mouth ulcers (larger than 1 cm or lasting longer than 2 weeks) may need to be treated with an antibiotic called tetracycline. (Tetracycline is usually not given to children until after all the permanent teeth have fully developed, because it can discolor still-forming teeth.)
Multiple, painful mouth ulcers may treated with an anti-viral medicine such as acyclovir.
Powerful anti-inflammatory medicines called corticosteroids are used in rare cases.
If you have a canker sore, you should not eat hot or spicy foods, which can cause pain. Mild, over-the-counter mouth washes or salt water may help. There are over-the-counter medicines that soothe the painful area. These medicines are applied directly to the sore area of the mouth.
To prevent bacterial infection, brush and floss your teeth regularly and visit the dentist for routine care.
To speed up healing, try mixing 1 part hydrogen peroxide and one part water and apply it to the canker sore with a cotton swab. Then dab a small amount of milk of magnesia on the canker 3 - 4 times a day. This also helps relieve discomfort.
Canker sores usually heal on their own. The pain usually decreases in a few days. Other symptoms disappear in 10 to 14 days.
Antibiotic treatment for canker sores may lead to oral thrush (a type of mouth infection) or other Candida infections. Rarely, bacterial infections such as cellulitis and Ludwig's angina may occur.
Mouth cancer is not a complication of canker sores, but if an ulcer lasts more that 2 weeks, you should see your doctor to rule out possible cancer.
Apply home treatment and call your health care provider if symptoms of canker sores persist or worsen, or canker sores recur more often than 2 or 3 times per year.
Call your health care provider if symptoms are associated with other problems such as fever, diarrhea, headache, or skin rash.