Updated on February 7, 2024
9 min read

Mouth Sores

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Mouth sores are painful ailments that appear on the soft tissues of your mouth, including the lips, cheeks, gums, tongue, and roof of your mouth. They affect your ability to eat, drink, practice dental hygiene, and talk. 

Mouth sores, including canker sores (aphthous ulcers), are typically harmless and last just a week or two.1 However, mouth sores may indicate oral cancer or a viral infection, such as herpes simplex virus (HSV), and in some cases, require professional care.2

What Causes Mouth Sores?

You can develop mouth sores from viral, fungal, or bacterial infections, or oral cancer. Other risk factors include:

  • Irritation to the mouth tissues 
  • Injury or trauma from external objects, such as orthodontic wires or sharp edges of broken teeth
  • Sensitivity to ingredients in toothpaste and mouthwashes
  • Reactions to medications or specific therapies, such as cancer treatment
  • Systemic disorders, such as oral lichen planus or inflammatory bowel disease
  • Tobacco use 
  • Exposure to irritants
  • Burns from hot foods or drinks
  • Acidic fruits
  • Spicy foods and drinks
  • Stress or lack of sleep
  • Tongue or cheek biting
  • Allergic response to certain foods or environmental elements
  • Nutritional deficiencies
  • Celiac disease

What Do Mouth Sores Look Like?

While mouth sores look different depending on the cause, they are typically a different color from surrounding tissue and can appear red, purple, yellow, or white.

They may develop on any of your mouth’s soft tissues, including your:

You may also have mouth sores and inflammation in your esophagus, the tube that connects your mouth to your stomach. A tingling or burning sensation may occur a day or two before the sores develop. The following images show different types of mouth sores: 

8 Types of Mouth Sores

1. Canker Sores

Canker sores, also called aphthous ulcers, develop within the oral cavity.3 They appear as small ulcers with a white, yellow, or gray center and a flat red border. Severe canker sores may sometimes have a large diameter and a raised edge.

afta labiale

Canker sores typically appear as a red lump or patch. Before additional symptoms emerge, a canker sore may cause a tingling or burning sensation. Fortunately, most heal on their own within 7 to 10 days.

There is limited research on the exact cause of canker sores. However, scientists have linked the condition to genetics. Other triggers include:

  • Fatigue
  • Stress
  • Mouth tissue trauma
  • Certain foods (citrus and acidic)

2. Cold Sores

Cold sores are painful, fluid-filled blisters that form in clusters (often called fever blisters) caused by the herpes simplex virus (HSV). These sores typically appear on the border of the lips, called the vermilion border.

illustration of infection on a womans lips known as oral herpes

HSV can spread through nonsexual contact, such as kissing, touching an infected person’s skin, or sharing infected objects like lip balm.

Once infected with herpes, the virus remains dormant in the body. Sores may appear when the virus reactivates and last 2 to 6 weeks.4 Several factors, including wind, sun, fever, or stress, can trigger a ‘flare-up.’ 

3. Candidiasis

Candidiasis, or oral thrush or moniliasis, is a yeast infection that causes creamy white and red spots on the mouth’s surfaces.5

Oral Candidiasis medical illustration

Candidiasis is caused by an overgrowth of candida fungus in the oral cavity. It is most common among the very young, the elderly, and people with a weakened immune system, such as patients with diabetes or AIDS. It is also common among denture wearers. 

This condition may be painful. It can also cause foul breath and trouble eating and swallowing.

4. Leukoplakia

Leukoplakia is a condition in which a white or gray patch develops on the mouth’s interior. It is caused by abnormal cell growth in the mouth lining. It typically appears under the tongue or on the inside of your cheeks. Patches of leukoplakia appear gradually and heal over time.


Leukoplakia differs from other causes of white spots as it can progress to oral cancer.

Common causes of these mouth sores include:6 

  • Smoking or chewing tobacco
  • Certain foods
  • Cheek biting
  • Irregular dental restorations
  • Damaged teeth 

5. Erythroplakia

Erythroplakia is a red, velvety lesion that may appear anywhere in the mouth. It is most often found on the gum tissue behind the back teeth or the floor of the mouth.7

The cause of erythroplakia is unclear, although it is most often linked to alcohol and tobacco consumption. Chronic inflammation and poor diet can also play a role. 

Erythroplakia is less common than leukoplakia. However, biopsies reveal that some of these sores are precancerous or malignant.8

6. Oral Cancer

White or red lesions, lumps, or ulcers in the mouth may all be signs of mouth cancer. Mouth cancer often starts small and painless but rapidly grows and spreads. 

Most oral cancers are detected during routine medical checkups. The sores from oral cancer may appear on the lips, tongue, gum, or the roof of your mouth.

Contributing factors to oral cancer include consuming cigarettes, smokeless tobacco, and alcoholic beverages. According to experts, 90 percent of all oral cancer cases are due to the use of tobacco products.9

7. Celiac Disease

Celiac disease is an autoimmune disease where the consumption of gluten, a protein found in wheat and other grains, damages the lining of your small intestine. People with celiac disease often experience outbreaks of canker sores or aphthous ulcers. The symptoms can improve by adopting a gluten-free diet.

8. Hand, Foot, and Mouth Disease

Hand, foot, and mouth disease (HFMD) is a viral illness common in children under five. It usually starts with a fever and rashes on the hands and feet. HFMD can also affect the mouth and tongue, causing mouth sores.

Hand Foot and Mouth disease symptoms medical illustrations

The viruses that cause HFMD spread quickly between people who come into close contact with each other. These viruses include:

  • Coxsackievirus A16
  • Coxsackievirus A6
  • Enterovirus 71 (EV-A71)

Mild symptoms of HFMD usually resolve within 7 to 10 days.

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Mouth Sores
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Other Symptoms of Mouth Sores

Mouth sores may cause difficulty eating, drinking, swallowing, speaking, or breathing, depending on the sores’ size, intensity, and location. They are typically painful and cause redness or tingling. Blisters may form on the sores.

Other symptoms associated with mouth sores, depending on the cause, can include:

  • Joint pains
  • Fever
  • Diarrhea
  • Frequent outbreaks
  • Swollen lymph nodes
  • Fatigue
  • Bleeding gums

How to Treat Mouth Sores

Most mouth ulcers will heal without treatment. However, if your mouth ulcers are frequent and painful, going to a healthcare provider or dentist is the best way to rule out any underlying issues. Treatment options include:

Professional Mouth Sore Treatments

When you see your doctor for mouth sores, they may prescribe a pain reliever, anti-inflammatory medicine, or steroid gel. If your mouth sores are caused by a viral, bacterial, or fungal infection, your doctor may prescribe antivirals, antibiotics, or antifungals to treat the disease.

Mouth sores can be treated with a low-powered laser, which provides instant pain relief and often prevents sores from recurring. Chemically burning the sore with a tiny stick coated in silver nitrate may similarly alleviate pain, though it is less effective than a laser.

Your doctor will order a biopsy for further examination if mouth cancer is suspected. If oral cancer is detected, your doctor will prepare a treatment plan, including surgery or chemotherapy.

Home Remedies for Mouth Sores

Mouth sores don’t always require a visit to your doctor, and if you’re dealing with minor pain, you can likely treat the ailment at home. The most effective home remedies for mouth sores include the following:

  • Gargle with salt water and baking soda – Baking soda can minimize the bacteria in the mouth, while a salt mixture can help dry out a mouth sore for quicker healing. If rinsing with salt water, mix one teaspoon (tsp) of salt with ½ cup of water, gargle, and rinse. If using baking soda, mix one part baking soda with one part water, gargle, and rinse. Do not swallow either mixture. 
  • Place milk of magnesia on the sores – Milk of magnesia can help to dry out the sores. Apply a small amount to the lesion several times a day. The medication will coat the mouth sore, relieving irritation and pain. 
  • Apply ice – Wrap an ice cup with a paper towel and hold it over the sore. Never put ice directly on the sore. This remedy will temporarily relieve any painful sensation caused by the sore. 
  • Take over-the-counter medications – Over-the-counter (OTC) medications, such as topical creams containing benzocaine and lidocaine, provide a protective layer over the sore to promote healing. 
  • Use mouth rinses containing a steroid for pain management – For a severe mouth sore, a steroid mouthwash containing the ingredient dexamethasone can assist with healing and prevent a mouth sore from worsening. 
  • Take supplements for nutritional deficiencies – Mouth sores are often found in people with nutritional deficiencies. Frequent mouth sores can indicate low zinc, folic acid, iron, and vitamin B12 levels. A blood test can rule out or confirm nutritional deficiencies.

When to See a Doctor for Mouth Sores

If your mouth sores occur frequently, it may be time to see a doctor. 

Seek immediate medical attention if you notice any of the following:

  • Non-painful sores in one or more areas of the mouth
  • Unusually large sores
  • Rapidly spreading sores
  • Sores that take longer than three weeks to heal 
  • A fever accompanying the mouth sores
  • Mouth sores developing after starting a new medication
  • Extreme difficulty eating or drinking

According to Dr. Nandita Lilly, one of NewMouth’s in-house dentists, “Mouth sores are a fairly common ailment among the population, and fortunately, your dentist may be able to help reduce pain, control the outbreaks, and even diagnose early signs of oral cancer.”  

How to Prevent Mouth Sores

Here are some tips for preventing mouth sores:

  • Practice good oral hygiene by brushing and flossing regularly
  • Avoid alcohol consumption
  • Use a toothbrush with soft bristles to prevent irritation 
  • See your dentist for regular dental checkups
  • Avoid spicy, salty, and acidic foods
  • Talk to your healthcare provider to find out if you have nutrient deficiencies that cause mouth sores


Mouth sores are usually harmless but can become serious if recurring or untreated. Many factors, including poor oral hygiene, physical trauma to the mouth, and certain diseases, can cause them. If your mouth sores don’t disappear within a few weeks, seek professional help immediately.

Last updated on February 7, 2024
10 Sources Cited
Last updated on February 7, 2024
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
  1. Canker sore.” Mayo Foundation for Medical Education and Research (MFMER).
  2. Herpes – oral.” National Institute of Health (NIH).
  3. Canker sore.” U.S National Library of Medicine (NLM).
  4. Wald A., and Corey, L. “Persistence in the population: epidemiology, transmission.” Cambridge University Press, 2007.
  5. Fungal Diseases: Candidiasis.” Center for Disease Control and Prevention (CDC).
  6. “Leukoplakia.” Mayo Foundation for Medical Education and Research (MFMER).
  7. Bedi, R., and Scully, C. “Manson’s Tropical Infectious Diseases (Twenty-third Edition).” Elsevier Ltd, 2014.
  8. “Erythoplakia: Causes, Symptoms & Treatment” Cleveland Clinic, 2023.
  9. Tobacco and Cancer” Center for Disease Control and Prevention (CDC).
  10. Mohammed F., and Fairozekhan, AT. “Oral Leukoplakia.” StatPearls Publishing, 2022.
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