Why a Canker Sore Won't Heal

Canker sores are red or white painful abrasions that occur on the inside of the cheeks, tongue or gums. Treat most stubborn canker sores at home. More stubborn canker sores my require medical attention.


The Mayo Clinic suggests that eating certain foods may cause and worsen canker sores, including coffee, chocolate, acidic foods, cheese, coffee, eggs, strawberries and nuts.

Time Frame

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A canker sore should heal on its own within one to two weeks, according to the Mayo Clinic.


Toothpastes containing sodium laureth sulfate, a foaming agent, may irritate the canker sore to the point where it will not heal and should be avoided.


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Braces and other dental work may irritate the canker sore, preventing it from healing. Use dental wax to cover sharp areas to promote healing.


Seek medical attention if your canker sores is so painful that you are unable to eat or drink. The doctor may prescribe a collagenase inhibitor or an anti-inflammatory medication that will decrease the healing time for canker sores.