How to Stop a Canker Sore at the Beginning

Canker sores are small lesions that usually appear inside of your lips, on your gums and under your tongue. Researchers have not found a viral cause, or any other definite canker sore cause. It is not always possible to stop canker sores from forming, but aggressive treatment in the early stages can sometimes speed healing. Treating canker sores as soon as you feel that first tingle may lessen the severity of the outbreak.

Close up of a teaspoon of baking soda about to be put into a glass of water. Credit: JPC-PROD/iStock/Getty Images

Step 1

Take daily supplements containing vitamin B-12, folic acid and iron. According to researchers at the National Institute of Dental and Craniofacial Research, British studies showed that 20 percent of patients who developed canker sores were deficient in vitamin B-12, folic acid and iron. Studies in the U.S. have been unable to verify these results, but vitamin B-12, folic acid and iron are all necessary for healthy red blood cells, which are necessary to carry the oxygen and nutrients needed for healing.

Step 2

Mix equal amounts of hydrogen peroxide and water. The experts at the University of Illinois, McKinley Health Center, recommend that you gargle with this mixture four times per day. If you cannot tolerate the taste, mix 1 tsp. each of baking soda and salt in 4 oz. of warm water and gargle with that instead. Both mixtures are somewhat drying, and may speed healing.

Step 3

Apply a dot of oral benzocaine to the tip of a clean cotton swab and massage into the tingling spot where the canker sore is trying to form. Benzocaine is found in over-the-counter treatments for fever blisters and cold sores, but it is also effective on canker sores.

Step 4

Soak a tea bag in warm water and squeeze out most of the moisture. Apply this to the tingling spot as a compress four times per day. The experts at University of Michigan Health Services suggest that any tea bag may help, but green tea has been shown to have soothing and anti-microbial properties.

Things You'll Need

  • Supplement containing vitamin B-12, folic acid and iron

  • Hydrogen peroxide

  • Salt

  • Baking soda

  • Cotton swabs

  • Topical benzocaine

  • Green tea bags (optional)


Treat yourself to Popsicles to soothe and cool the irritated skin inside of your mouth.


Avoid fresh citrus, foods that are salty or spicy, and hot drinks while your canker sore heals.

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