Canker Sore (Aphthous Ulcer)
Written by WebMD Editorial Contributors
Medically Reviewed by Sabrina Felson, MD on May 12, 2021
In this Article
- What Is a Canker Sore?
- Canker Sore Causes and Risk Factors
- Canker Sore vs. Cold Sore
- Canker Sore Symptoms
- Canker Sore Diagnosis
- Canker Sore Treatment
- Canker Sore Home Remedies
- Canker Sore Prevention
A canker sore is a small, shallow open wound (or ulcer) in your mouth that can make eating and talking uncomfortable. They’re also known as aphthous ulcers. There are a few types of canker sores:What Is a Canker Sore?
- Minor canker sores. These may show up three or four times a year. They typically happen in people ages 10 to 20. They’re less than 1 centimeter across and heal in about a week with no scarring.
- Major canker sores. These are less common. The ulcers are bigger and can last more than 2 weeks. They often heal with scarring.
- Herpetiform canker sores. These are rare and show up as clusters of tiny ulcers. They usually heal in about a week.
Canker Sore Causes and Risk Factors
Doctors don’t know what exactly causes most canker sores.
Things that might cause minor sores include:
- Stress
- Tissue injury, like from a sharp tooth or a dental appliance
- Certain foods, including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, and strawberries)
- Nonsteroidal anti-inflammatory drugs like ibuprofen
- An allergy to something in your food or in your toothpaste or mouthwash
- Helicobacter pylori, the bacteria that can cause peptic ulcers
Things that might cause complex canker sores include:
- An underlying health condition like a weakened immune system, HIV/AIDS, lupus, or Behcet’s disease
- Nutritional problems like too little vitamin B12, zinc, folic acid, or iron
- Gastrointestinal diseases like celiac or Crohn’s
About 1 in 5 people gets canker sores regularly. They’re more common in women, possibly because of hormonal differences. They may also run in families.
Canker Sore vs. Cold Sore
Canker and cold sores aren’t the same.
Cold sores, also called fever blisters or herpes simplex type 1, are groups of painful, fluid-filled blisters. Unlike canker sores, a virus causes cold sores, and they’re highly contagious. Also, cold sores typically appear outside your mouth -- usually under your nose, around your lips, or under your chin -- but canker sores show up inside your mouth.
You may have a canker sore if you have: Severe canker sore attacks may also cause: Canker sores usually aren’t serious. Call your dentist if you have:Canker Sore Symptoms
Canker Sore Diagnosis
- Unusually large sores
- Sores that spread
- Sores that last 3 weeks or longer
- Extreme pain despite avoiding trigger foods and taking over-the-counter pain medication
- Trouble drinking enough fluids
- A high fever with canker sores
- Frequent or lasting mouth sores, which may be a sign of an underlying problem, such as a serious skin disorder called pemphigus, celiac disease, inflammatory bowel disease, Behcet's disease, autoimmune disease, anemia, HIV, or, in rare cases, oral cancer or leukemia
They can usually make a diagnosis based on a physical exam and your medical history. They might want to test your blood to see whether a vitamin deficiency or another health condition is causing the sores.
Canker Sore Treatment
Pain from a canker sore tends to get better in a few days, and the sores usually heal without treatment in about a week or two. Treatment for large, long-lasting, or unusually painful sores might include:
- Mouthwashes. Your doctor can prescribe a rinse that has a steroid or a painkiller.
- Topical medications. Your doctor may prescribe a topical medication containing a steroid for the inflammation, and a topical analgesic like lidocaine to relieve pain. Aphthasol, a prescription ointment described as an "oral paste," may reduce pain and healing time.
- Oral medications. The ulcer drug sucralfate (Carafate) and the gout drug colchicine (Mitigare) can also treat canker sores. Or your doctor might give you steroid pills.
- Nutritional supplements. You might need these if a nutrient deficiency is causing your canker sores.
- Cautery. Dental lasers can help you feel better right away. Your doctor can also cauterize sores with chemicals like debacterol or silver nitrate.
Home treatments to speed healing and help you feel better include: There’s no cure for canker sores, and they often come back. But you might get them less often if you:Canker Sore Home Remedies
Canker Sore Prevention
What kills canker sores fast?
Why is my canker sore so painful?
How long does it take for a canker sore to stop hurting?
How do you numb a canker sore?