What is a mouth ulcer?

Mouth ulcers, or canker sores, are blisters that appear in the lining of the mouth and tongue. There is no cure for canker sores, but painkillers, antimicrobial mouthwash, numbing sprays and corticosteroid lozenges may provide relief.
Mouth ulcers, or canker sores, are blisters that appear in the lining of the mouth and tongue. There is no cure for canker sores, but painkillers, antimicrobial mouthwash, numbing sprays and corticosteroid lozenges may provide relief.

Many people get mouth ulcers sometimes called canker sores or aphthous ulcers. These are a sore or blister that appears in the lining of the mouth and sometimes on the tongue. Mouth ulcers are not serious and usually clear up on their own.

A mouth ulcer is a hole in the lining of the mouth that develops when the top layer of cells breaks down. Some may be red, but some can also turn white as dead cells and food get in the center. A blister can also appear as a raised sore filled with clear fluid. 

Symptoms

Some symptoms of mouth ulcers include:

  • Blister or sore with a red border and white center
  • Found inside the mouth on the lips, cheeks, tongue, and roof of mouth
  • Pain even when you’re not eating
  • Pain when you eat certain foods like citrus fruits or spicy foods
  • Tingling, burning, or rough feeling as the blister develops
  • One sore or two or three together

Mouth ulcers are often confused with cold sores. However, cold sores are caused by the herpes simplex virus and appear on the outside of the mouth around the lips. 

Causes of mouth ulcers

Experts don’t know the exact reason why people develop mouth ulcers, but there may be some things that contribute. These may include:

Who can get mouth ulcers

Anyone can get mouth ulcers, but women are more likely to develop mouth ulcers, especially while pregnant or during the menstrual cycle. While children can develop a mouth ulcer, most people develop them for the first time as a teenager or young adult. 

People being treated with chemotherapy may develop mouth ulcers. It can range from some sores to severe inflammation, bleeding, and ulceration called mucositis.

Diagnosis for mouth ulcers

You may not need to see your doctor about a mouth sore unless they are persistent, you have other symptoms, or you are feeling very unwell. Your doctor will take your personal and medical history and do a physical exam to look at your sores. 

Your doctor may look to see if you have large white patches on the roof of your mouth to rule out an infection called thrush or for signs of other conditions.

Your dentist can also examine your mouth and diagnose your mouth ulcers during annual checkups and cleanings. 

Remedies for mouth ulcers

There are no quick fixes for mouth blisters as they need time to heal, but they will usually resolve on their own without treatment. The blisters may be sore for seven to 10 days. Minor blisters will heal in one to two weeks, but major canker sores can take up to four weeks. 

While mouth blisters usually heal on their own without treatment, you may be uncomfortable and feel pain. You can manage your mouth blisters at home with over-the-counter medications and self-care practices.

What treatments can help?

You can manage your symptoms with some over-the-counter medications, including:

If your canker sores are very uncomfortable, or persistent and don’t respond to home treatment, your doctor may prescribe steroid cream to rub on the blister or canker sore and a prescription mouthwash. They may also recommend vitamins if you are lacking vitamin B12 and iron.

What are some natural home remedies for mouth ulcers?

Managing your symptoms at home will help your blisters heal and ease your discomfort. There are some natural home remedies you can try, including:

  • Rinse your mouth with warm saltwater
  • Drink cold fluids instead of hot drinks like coffee or tea
  • Eat popsicles
  • Numb the sore with an ice cube or suck on ice
  • Eat soft, bland foods 
  • Use a toothbrush with soft bristles
  • Apply a thin paste of baking soda and water to the blister
  • Apply hydrogen peroxide and water to the blister
  • Apply milk of magnesia to the blister

What are some alternative therapies for mouth ulcers?

Low level laser therapy can relieve mouth blisters in severe or chronic situations.

Risks and outlook

Mouth ulcers generally are not serious and heal on their own without treatment. However, you may need to see your doctor if:

  • You have trouble eating or drinking
  • They keep coming back
  • You are feeling very unwell
  • You have other symptoms
  • They don’t respond to treatment
  • They become more painful and red

What causes and how do you treat a canker sore on your gums?

Canker sores are ulcers that can appear in the mucous membrane lining of the mouth. Most often, they form inside the cheeks, but they can sometimes form on the roof of the mouth, tongue, or on the gums, too. There's typically a burning or tingling sensation when one of these sores — also known as an aphthous ulcer — is forming. A minor canker sore is red, slightly raised, and usually, just a few millimeters wide, while major ones are much larger and more painful.

Canker sores usually do heal on their own. It’s unknown why these non-contagious sores develop, so there’s no definitive treatment for them. But some preventative tips can help you avoid recurrent ones.

Causes of canker sores

Ultimately, it isn’t known why some people develop canker sores while others don't. Some believe that predisposition to develop canker sores is hereditary while others believe certain factors influence how often someone gets them. A few suspected causes of canker sores include:

  • Trauma to the mouth lining: Whether it's biting your cheek, a cut from your braces, or brushing your teeth too hard, any of these can cause a mouth ulcer to form.
  • Food sensitivity: Some ulcers are triggered by acidic foods found in citrus fruit, tomatoes, and even coffee.
  • Vitamin deficiencies: Having low levels of B-12, folic acid, iron, or zinc may cause mouth ulcers.
  • Kinds of toothpaste or mouthwash: Using toothpaste or mouthwash with sodium lauryl sulfate has been proven to irritate the mouth lining and gums.
  • Hormonal changes: This can affect how blood flows to gum tissue, but also how the body responds to toxins. Women are more prone to develop oral health problems and canker sores due to hormonal fluctuations.
  • Autoimmune disease: Conditions such as ulcerative colitis, inflammatory bowel disease, or Crohn’s Disease may cause the onset of canker sores.

Is it a cold sore or a canker sore?

Sometimes, it’s hard to determine whether you have a cold sore or a canker sore. Generally, canker sores do not appear on the outside of the lips or mouth. While both have the same triggers, canker sores aren’t contagious and there is no bacteria or virus associated with them unlike cold sores.

Also known as fever blisters, cold sores are fluid-filled sores that occur around the lips. Some people develop a fever, swelling of the lymph nodes, or fatigue when they have one. This is most likely due to the bacteria or virus that caused them. Unlike canker sores, cold sores are usually treated with prescription antivirals and rarely go away without treatment. If you think you have a cold sore, schedule an appointment to see your doctor.

Diagnosing a canker sore

Your doctor will first review your medical history to determine if you have any active medical conditions that may increase your risk of developing mouth ulcers. To confirm a canker sore diagnosis and to rule out other possible causes for ulcers, your doctor may order:

  • Lesion cultures
  • Blood tests
  • Biopsy of the sore

While most canker sores are harmless, some mouth ulcers may be caused by drug allergies, herpes infection, erythema multiforme, or bullous lichen planus. This makes it important to be examined by your doctor when you experience canker sore symptoms.

Canker sore treatment

Canker sore treatment depends on your medical history, the extent of the sores, and the symptoms you’re experiencing. Some canker sore treatments include:

  • Antimicrobial mouthwash
  • Corticosteroid throat lozenges
  • Pain-relieving mouthwash, gel, or spray
  • Saline rinse

If your canker sore symptoms don’t resolve after a week of your treatment, schedule an appointment with your doctor.

Tips to prevent canker sores

While it’s impossible to completely eliminate canker sores, there are some things you can do to help prevent them from occurring often, like:

  • Using a soft toothbrush to prevent irritation of the mouth’s lining.
  • If you have braces, using orthodontic wax to cover any sharp edges that may lead to trauma.
  • Finding effective stress-reduction techniques, such as yoga or meditation.
  • Keeping a food diary, so you can draw connections between what you eat and whether it caused you to develop a canker sore.

When to see a doctor

When a canker sore is very large, lasts several weeks, moves to the lips, or you develop a fever, it’s time to see your doctor. Also, if you’re older and are developing one for the first time, it may indicate another health issue, which requires medical treatment.

Subscribe to MedicineNet's General Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

Health Solutions From Our Sponsors

Medically Reviewed on 3/1/2022
References
American Cancer Society: "Mouth Sores and Pain."

InformedHealth.org, Institute for Quality and Efficiency in Health Care, 2006.

MedlinePlus: "Canker sore."

Merck Manual: "Mouth Sores and Inflammation."

National Health Service: "Mouth ulcers."

The Pan African Medical Journal: "Low laser therapy as an effective treatment of recurrent aphthous ulcers: a clinical case reporting two locations."

Cedar Sinai: “Everything You Ever Wanted to Know About Canker Sores.”

Cincinnati Children’s: “Aphthous Stomatitis (Canker Sores).”

Cleveland Clinic: “Hormones and Oral Health.”

National Center for Biotechnology Information, U.S. National Library of Medicine: “Canker sores (mouth ulcers): Overview.”

National Health Service England: “Mouth ulcers.”

National Institute of Dental and Craniofacial Research: “Fever Blisters & Canker Sores.”

University of Florida Health: “Canker sore.”