Top of the page
A canker sore is a shallow sore shaped like a crater (ulcer) on your tongue or on the inside of your lip or cheek. Canker sores have a red border and a white or yellow centre. They may be painful and can make it hard to talk and eat. You may have one or more than one canker sore at a time. Unlike cold sores, you cannot spread canker sores to other people.
Anyone can get a canker sore, but women, teens, and young adults have them more often. Most people have canker sores at some time in their lives, and some people have them regularly.
The cause of canker sores is unknown, but they tend to run in families. Canker sores are not contagious.
Canker sores may also develop when you:
The main symptom of a canker sore is getting a shallow ulcer on your tongue or on the inside of your lip or cheek. The sore may be large or small, and it will have a red border and a white or yellow centre. You might have more than one canker sore at a time.
Canker sores usually begin with a burning or tingling feeling. They may be swollen and painful. Having a canker sore can make it hard to talk or eat.
Canker sores may hurt for 7 to 10 days. Minor canker sores heal completely in 1 to 3 weeks, but major canker sores can take up to 6 weeks to heal. Some people get another canker sore after the first sore has healed. Most canker sores heal without a scar.
If you see your doctor or dentist about the pain caused by your canker sores, he or she will do a physical examination by looking in your mouth to diagnose the canker sores.
You do not need to see a doctor for most canker sores. They will get better on their own. There are many things you can try at home to relieve the pain caused by your canker sores:
If your canker sores do not feel better after trying these steps at home for 2 weeks, you may need to see your doctor or dentist. He or she may recommend medicines that will help relieve pain caused by your canker sores. Usually these medicines are swished or gargled in your mouth, or they are painted on the sore. Your doctor may prescribe steroid cream or paste to rub on your canker sore and/or a prescription mouthwash to use.
Talk to your doctor if you have a fever, have trouble swallowing, or if your canker sores keep coming back. You may have another problem that is causing your symptoms.
Most of the time the cause of canker sores is unknown. Unless you know what causes your canker sores, you cannot prevent them from happening. If you do know what causes your canker sores, you can help prevent them by avoiding what you know causes them. For example, if you have gotten canker sores in the past from hurting the inside of your mouth, you might help prevent them by chewing your food slowly and carefully, trying not to talk and chew at the same time, and using a soft-bristled toothbrush when you brush your teeth.
If you have gotten canker sores in the past by eating foods that have a lot of acid (such as citrus fruits or tomatoes) and sharp or harsh foods (such as bread crusts, corn chips, or potato chips), it might help to avoid these. Other ways that might help to prevent canker sores include limiting your use of alcohol and tobacco and controlling the stress in your life.
In general, it is important to get enough vitamins and minerals in your diet, like folic acid, vitamin B12, zinc, and iron.
Current as of: June 30, 2021
Author: Healthwise StaffMedical Review: Kathleen Romito MD - Family MedicineAdam Husney MD - Family MedicineE. Gregory Thompson MD - Internal MedicineMartin J. Gabica MD - Family Medicine
Current as of: June 30, 2021
Author: Healthwise Staff
Medical Review:Kathleen Romito MD - Family Medicine & Adam Husney MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Martin J. Gabica MD - Family Medicine
To learn more about Healthwise, visit Healthwise.org.
© 1995-2021 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.