A canker sore is a small, shallow open sore inside the mouth that usually heals on its own within one to two weeks. There is no home remedy that makes a canker sore disappear overnight, but several approaches can ease pain and may shorten how long it lasts. The most reliable options are saltwater or baking soda rinses, avoiding acidic and spicy foods, and using over-the-counter products that coat the sore. If a sore lasts longer than two weeks or keeps coming back, see a doctor or dentist.
What Exactly Is a Canker Sore?
A canker sore is a break in the lining of the mouth. It is not the same as a cold sore.
Cold sores are caused by the herpes simplex virus and usually appear on the outside of the lips. Canker sores form inside the mouth — on the tongue, the inside of the cheeks or lips, the soft palate, or the base of the gums. They are not contagious.
Most canker sores are round or oval with a white or yellow center and a red edge. They typically measure a few millimeters across. Minor canker sores, the most common type, are small and heal without scarring. Larger ones, called major canker sores, are less common and can take longer to heal and may leave a scar.
Roughly 1 in 5 people get canker sores regularly, according to estimates cited in dental and medical literature. They are more common in women, in teens and young adults, and in people with a family history of them.
What Causes Canker Sores?
The exact cause is not fully understood. Researchers believe canker sores are not one disease but a reaction with several possible triggers.
Common triggers include:
- Minor mouth injury from dental work, braces, a sharp tooth edge, or accidental biting
- Certain foods, especially acidic or spicy ones like citrus, tomatoes, and chili
- Stress and lack of sleep
- Toothpaste or mouthwash containing sodium lauryl sulfate, a foaming agent
- Stopping smoking, in some people
- Hormonal changes, including around menstruation
- Nutritional deficiencies in vitamin B12, folate, iron, or zinc
- Certain medications, including some pain relievers and beta-blockers
Some people get canker sores as part of a broader condition. Celiac disease, Crohn’s disease, ulcerative colitis, Behçet’s disease, and HIV can all cause recurrent mouth ulcers. So can a weakened immune system. If sores are frequent or severe, that possibility is worth discussing with a doctor.
How To Fix a Canker Sore Fast With Home Remedies That Help
No home remedy is proven to cure a canker sore instantly. What the evidence supports is reducing pain and possibly shortening the healing time. Here is what has reasonable backing.
Saltwater and baking soda rinses
Dissolve about half a teaspoon of salt in a cup of warm water, or mix a similar amount of baking soda into water. Swish gently and spit. These rinses do not kill the sore, but they clean the area and can reduce irritation. Many dentists suggest them as a first step. Do not swallow the rinse, and do not use very hot water.
Avoiding trigger foods
Acidic, salty, and spicy foods can make a canker sore hurt more and may slow healing by irritating the tissue. During a flare, it can help to skip citrus, tomatoes, vinegar, chili, and salty snacks. Cool, soft foods tend to be easier to tolerate.
Over-the-counter protective gels and rinses
Products that form a protective coating over the sore can reduce pain while eating and talking. Some contain a mild anesthetic. These do not speed healing, but they make the sore more bearable. Follow the label directions, and do not use them for longer than the package states.
Honey
Some small studies suggest honey may help mouth sores heal, likely because of its antibacterial and soothing properties. The evidence is limited and the studies are small. It is unlikely to cause harm for most people, but it is not a proven treatment.
Ice and cold liquids
Holding a piece of ice against the sore or sipping cold water can numb the area and reduce pain for a short time. This is a comfort measure, not a treatment.
One clarification worth making: despite what circulates online, there is no strong evidence that vitamin supplements speed healing in people who are not deficient. If a blood test shows a deficiency in B12, folate, iron, or zinc, correcting it may help. Taking those supplements without a deficiency is unlikely to make a difference.
Which Remedies Do Not Have Good Evidence?
A lot of advice about canker sores spreads faster than the evidence behind it. Here is an honest look at some popular claims.
- Alum powder: Sometimes suggested to dry out a sore. It can irritate tissue and there is no good evidence it helps.
- Hydrogen peroxide: Can damage healthy tissue and delay healing. Not recommended.
- Apple cider vinegar: Acidic and likely to make the sore worse, not better.
- High-dose vitamin C: Acidic and irritating. No evidence it speeds healing.
- Toothpaste on the sore: Can irritate the tissue. Not a treatment.
If a remedy sounds like it would sting or burn, that is a sign it may do more harm than good.
When Should You See a Doctor About a Canker Sore?
Most canker sores heal within one to two weeks without treatment. See a doctor or dentist if:
- A sore lasts longer than two weeks
- Sores are unusually large or spreading
- You get them very often, or new ones appear before old ones heal
- You have trouble eating, drinking, or swallowing
- You also have fever, weight loss, or other symptoms
These signs can point to a nutritional deficiency, an immune condition, or in rare cases something more serious. A doctor can examine the sore and, if needed, order blood tests. A persistent sore that does not heal should always be checked — that rule applies to any mouth sore, not just typical canker sores.
Can You Prevent Canker Sores From Coming Back?
If you get canker sores often, some changes may reduce how frequently they appear. The evidence for prevention is not strong, but these steps are low-risk and often suggested.
- Switch to toothpaste without sodium lauryl sulfate
- Identify and avoid your personal trigger foods
- Manage stress where you can
- Get enough sleep
- Keep up with dental care to smooth any sharp teeth or dental work that irritates your mouth
- Ask a doctor whether a blood test for B12, folate, iron, or zinc is worth doing
None of these is guaranteed to stop canker sores. But they are reasonable steps, and the toothpaste change in particular has some supporting evidence for people who get recurrent sores.
What About Prescription Treatments?
For severe or frequent canker sores, a doctor or dentist may prescribe a stronger treatment. Options include a corticosteroid gel or rinse to reduce inflammation, or in some cases a prescription mouth rinse. These are typically reserved for sores that are large, painful, or keep coming back.
Prescription treatments are not first-line for a typical minor canker sore. They are for cases where home care is not enough. A clinician decides which, if any, is appropriate based on how often you get sores and how severe they are.
Frequently Asked Questions
How long does a canker sore take to heal?
Most minor canker sores heal within one to two weeks without treatment. Larger or more severe sores can take longer and may leave a scar.
What is the fastest way to get rid of a canker sore?
There is no way to make a canker sore disappear overnight. Saltwater or baking soda rinses, protective gels, and avoiding trigger foods can reduce pain and may help it heal a little faster.
Are canker sores contagious?
No. Canker sores are not contagious, unlike cold sores, which are caused by a virus and can spread through contact.
When should I worry about a canker sore?
See a doctor or dentist if a sore lasts longer than two weeks, is unusually large, or comes with fever, weight loss, or trouble swallowing. A sore that does not heal should always be checked.
