Canker Sores: Why They Happen and How to Treat Them

Canker sores—also called aphthous ulcers—are appropriately named: In Greek, aphthae (root of aphthous) means “to set on fire.”

Most people get canker sores from time to time. Some people get them over and over, known as recurrent canker sores.

Either way, anyone who has ever had a canker sore wants to get rid of it as quickly as possible. We talked to a Cedars-Sinai doctor to find out where canker sores come from, how to avoid them and what to do if you get one.

What Are Canker Sores?

Canker sores are small, painful sores that appear inside the mouth on the lips, cheeks, gums and tongue. These mouth ulcers are typically white or yellow with a red border. Some people notice a burning or tingling sensation in their mouth right before they appear.

While canker sores are not life threatening, they can be very painful.

Minor canker sores—sores that are smaller than 1 centimeter in diameter—typically heal quickly.

Major canker sores—sores that are bigger than 1 centimeter in diameter—can take along time to heal and may cause scarring.

Herpetiform canker sores are clusters of many tiny white sores. This type of canker sore is much less common than minor or major canker sores.

Why Do I Keep Getting Canker Sores?

No one knows for sure what causes canker sores. They often appear seemingly out of nowhere.

Unlike cold sores, canker sores are not contagious and can’t be spread through saliva.

Most people who get recurrent canker sores will get them two to three times a year, on and off, starting by the time they’re 30 years old.

Canker sores can run in families. If your parents or siblings get recurrent canker sores, you are more likely to develop them.

Common Triggers and Causes of Canker Sores

Canker sores can be triggered by a number of things, including:

• Injury to the mouth, such as accidentally biting your tongue or when braces rub against the inside of the cheeks or back of the lips
• A weakened immune system due to conditions such as herpes, HIV and inflammatory bowel disease
• Dehydration
• Allergies
• Stress
• Specific medications, including beta-blockers, nonsteroidal anti-inflammatory drugs and drugs that suppress the immune system
• Hormonal shifts during a woman’s menstrual cycle
• A lack of vitamin B12, zinc, folic acid or iron in your diet
• Sensitivity to chocolate, coffee, strawberries, eggs, nuts, cheese, or spicy or acidic foods
• Toothpaste containing sodium lauryl sulfate

Canker Sore vs. Cold Sore: What’s the Difference?

Canker sores and cold sores are different types of mouth sores.

Cold sores occur outside the mouth on the external surface of the lips. Canker sores appear inside the mouth on the internal surface of the lips, cheeks, gums and tongue.

Cold sores are contagious and are caused by herpes simplex virus type 1 (HSV1). Canker sores are not contagious. There is no virus or bacteria associated with canker sores.

How to Get Rid of Canker Sores

Minor canker sores tend to go away on their own within 10 days. Over-the-counter or prescription medications can be used to ease pain and speed along the healing process.

Rinsing your mouth with saltwater can help relieve some of the discomfort associated with canker sores.

How to Prevent Canker Sores

The best way to get rid of canker sores is to avoid getting them in the first place. Here are some tips to help you avoid canker sores:

• Brush your teeth and floss after meals
• Use a soft toothbrush to avoid irritating your mouth and gums when brushing your teeth
• Use orthodontic waxes to cover any sharp edges on braces, retainers or other dental devices
• Practice stress-management techniques, such as meditation
• Keep a food diary to help find connections between when canker sores appeared and what you ate

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“I’d also stay away from mouthwashes that contain alcohol,” said Nitin Kapur, MD, a Cedars-Sinai primary care doctor. “We all like that minty taste, but alcohol-based mouthwash can cause a lot of irritation in the mouth.”

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When Should You See a Doctor for Canker Sores?

Seek the advice of your primary care doctor or dentist if:

• The canker sore is more than 1 centimeter in diameter (bigger than a pea)
• The canker sore lasts two weeks or more
• The canker sore extends to the lips
• The canker sore makes it difficult to eat or drink
• The canker sore is accompanied by a fever
• You are over 30 years old and getting a canker sore for the first time

“Most people who get recurrent canker sores will get them two to three times a year, on and off, starting by the time they’re 30 years old,” said Kapur. “But if you’re older and you get a canker sore for the first time, that may be an indication something else is going on, so you’ll want to seek medical advice.”