Canker sores – Symptoms, Causes, and Treatment 

Canker sores or mouth ulcers (also called aphthous ulcers) are typically small, painful lesions that can develop on the soft tissues inside your mouth or at the base of your gums.

Although they’re not contagious and usually heal on their own in one or two weeks, they can cause discomfort when you’re eating, drinking, or talking.

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Canker Sores vs. Cold Sores

People often confuse canker sores with cold sores, but they’re not the same. Cold sores first appear as blisters and only become sores after the blisters pop. Unlike canker sores, cold sores are contagious. They’re caused by certain strains of the herpes simplex virus.

This virus stays in your skin and can become active if factors such as stress, exhaustion, or getting a cold temporarily weaken your immune system.

Also, unlike canker sores, cold sores usually appear outside the mouth – on the lips, around the lips and under your nose, or in your eyes.


The cause of canker sores has yet to be identified, but there are a few factors that seem to contribute to outbreaks:

  • A diet lacking in some essentials nutrients like vitamin B-12, folate, zinc, and iron
  • Helicobacter pylori – a type of bacteria that also causes peptic ulcers
  • Toothpaste and mouth wash that contains sodium lauryl sulfate
  • Sensitivity to certain foods like eggs, cheese, nuts, chocolate, coffee, spicy and acidic foods
  • Wearing braces
  • Minor injuries caused by accidentally biting the inside of your cheeks, overzealous brushing, or dental work
  • Hormonal shifts triggered by menstruation
  • Stress

Canker sores can also be a sign of a more serious condition requiring medical attention:

  • Celiac disease
  • Inflammatory bowel disease
  • Diabetes
  • Behcet’s disease – a rare disorder that causes inflammation of the blood vessels and tissues throughout the body
  • Malfunctioning immune system – the immune system attacks healthy cells instead of pathogens

Canker sores are not associated with the herpes simplex virus.

Risk Factors

Anyone can develop canker sores, but they are most common among teens and young adults. Also, women get them twice as often as men because of hormonal changes during menstruation.

Around 20% of people get canker sores regularly, and they have a family history of recurrent aphthous stomatitis (RAS). This may be due to genetic factors or shared environment, such as being exposed to the same allergens.


There are three types of canker sores with different symptoms.

Minor Canker Sores (Minor Aphthous Stomatitis)

About 80% of people get this form, and it’s most common between the ages of 10 and 20. You’ll see small round or oval ulcers – less than 1 centimeter across. They heal on their own in about a week without any scarring.

Major Canker Sores (Major Aphthous Stomatitis)

This form is more severe and accounts for about 15% of cases. The ulcers are larger than 1 centimeter with irregular edges. Since they’re also deeper, they can be very painful. Usually, they take longer than two weeks to heal (up to six weeks) and often result in scarring.

Herpetiform Canker Sores (Herpetiform Aphthous Stomatitis)

This form is uncommon and accounts for less than 5% of cases. The ulcers are very small (pinpoint size) and appear in clusters of ten to a hundred. They usually heal in about a week without scarring.

Note that even though the name contains the same word root as herpes, herpetiform canker sores are not caused by the herpes virus. The name is due to the similarity in appearance.

When Should I See a Doctor?

Cankers sores usually don’t require a visit to the doctor because they’re not contagious, and they heal on their own. If they’re causing you discomfort, you can also try natural remedies for mouth ulcers.

However, as mentioned earlier, they can be indicative of a more serious condition that requires medical attention. You should see a doctor if:

  • The ulcers don’t heal after more than two weeks
  • You get new ulcers before the old ones had a chance to heal
  • Your ulcers are unusually large
  • They extend outside the mouth, to the lips
  • They’re accompanied by high fever or diarrhea
  • Your ulcers are either painless, or they cause so much pain that it can’t be controlled with natural remedies or over-the-counter medication
  • They cause significant problems when you’re trying to eat or drink

Your doctor can usually diagnose them through a visual exam, but if they are frequent or severe, they will conduct further tests to check for bacterial or viral infections, vitamin or mineral deficiencies, problems with your immune system, or hormonal disorders.


The more common types of canker sores don’t require any treatment. The pain usually subsides in a few days, and they heal on their own in about a week. You can reduce the discomfort through home remedies.

However, if your sores are more severe and you decide to see a doctor, and they don’t find any serious underlying medical issue, they might prescribe:

  • Nutritional supplements – in case your canker sores are the result of a deficiency
  • Prescription mouthwash that contains lidocaine or dexamethasone to reduce the pain and inflammation
  • Oral medications
  • Corticosteroid ointments
  • Cautery – your doctor can cauterize your sores with chemicals like silver nitrate and Debacterol, or they can use dental lasers.

For less severe cases, the most common home remedies include:

  • Rinsing your mouth with a mixture of water, salt, and baking soda
  • Applying milk of magnesia to the ulcer
  • Applying ice
  • Applying damp teabags
  • Rinsing your mouth with chamomile tea or mouthwash with antimicrobial properties like Listerine

There are also a few things you can do to prevent canker sores:

  • If you wear braces, you can talk to your dentist about getting orthodontic wax to cover any sharp ages and prevent lesions
  • Maintain good oral hygiene by brushing your teeth after every meal and using dental floss at least once a day
  • Use a toothbrush with soft bristles and avoid toothpaste that contains sodium lauryl sulfate
  • Eat a healthy diet to prevent nutritional deficiencies
  • Reduce your stress and get plenty of sleep, which helps strengthen your immune system and your overall health
  • If you’ve noticed that your outbreaks are triggered by some acidic, spicy, or salty foods, avoiding them would also be helpful.


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