Mouth Lesions: Symptoms, Causes, Diagnosis, Treatment, and Prevention
Health ConditionsDental & Oral HealthOral Health

What Are Mouth Lesions?

What Are Mouth Lesions?
Everyday Health
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Updated on October 13, 2025
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If you notice a stinging sensation and redness on your upper or lower lip, you may know what’s coming: a cold sore. Or maybe you have a canker sore — one painful enough that it makes enjoying a meal difficult.

Whatever their type or origin, most of us have experienced painful sores on the mouth, lips, tongue, and inner cheek. And while they rarely call for a trip to the doctor, they can be embarrassing, especially if they are visible.

Types of Mouth Lesions

There are two main types of mouth lesions:

  • Cold sores
  • Canker sores

Cold sores — also called fever blisters — are caused by herpes simplex virus 1. You might hear them called oral herpes, and they occur around and in the mouth. They’re contagious.

Unlike cold sores, canker sores, which occur mainly inside the mouth, are not contagious. Their exact cause is unknown, but minor injuries caused by biting or gnashing are known triggers. They develop on the tissues in the mouth or at the base of the gums, and they can be quite painful.

Signs and Symptoms of Mouth Lesions

A person with a mouth or tongue lesion may have the following inside or outside of their mouth and lips:

  • Lumps
  • Bumps
  • Little ulcers
  • Cuts

The first thing to do is to identify the problem, since there are different types of sores.

Use a bright light and a magnifying mirror to examine the inside of your mouth, including sticking out your tongue to check for lacerations or swelling on the top, bottom, and sides. Look for any redness, shininess, or swelling in the mouth, on the gums, or on or under your tongue. You may also see white patches or pus in your mouth.

You’ll know you have a canker sore if you see a red ring around a white or yellow center. They tend to be small — less than 1 millimeter — but they may be up to 1 inch in diameter. Canker sores form on or under your tongue, inside your cheeks or lips, at the base of your gums, or at the back of the roof of your mouth.

Simple or minor canker sores may appear several times a year and last about a week. Major or complex canker sores, which are less common, are larger, deeper, and could take months to heal.

If you have numerous tiny canker sores with irregular edges, they’re called herpetiform canker sores. (Although the name seems to suggest it, herpes doesn’t cause them.) These are much less common, and they usually clear up within a few weeks.

Cold sores are small blisters filled with fluid that appear on or around the lips. You can often feel a cold sore coming on before it shows up. Symptoms can include:

  • Tingling or burning in the area
  • Sore throat
  • Oozing and crusting of the blister
  • Fever
  • Headache
  • Painful gums

Causes and Risk Factors of Mouth Lesions

The exact cause of canker sores is unknown, but possible triggers can include:

  • Grinding or clenching your teeth, especially while sleeping
  • Biting your tongue or chewing your lips
  • Brushing or flossing too vigorously or using a hard toothbrush
  • Drinking hot liquids
  • Minor injury to the mouth due to sharp or broken teeth or braces with protruding wires
  • Food sensitivities, including acidic or spicy foods
  • Hormonal shifts
  • Stress
  • Lack of sleep
  • Vitamin deficiencies
  • Gum disease
Sores on the tongue or inside the mouth may be caused or exacerbated by infections, inflammation, and stress.

Often, people with recurrent canker sores have a family history of them. They are also linked to rheumatologic conditions like lupus. (See below for other related conditions.)

Additionally, deficiencies of the following nutrients may lead to canker sores:

Cold sores, because they’re a form of herpes, are transmitted by oral-to-oral contact and through saliva, which means you can develop them through kissing or by sharing utensils with someone who has a cold sore.

This type of herpes virus can also be transmitted to the genitals through oral-genital contact and cause genital herpes. (Herpes simplex virus 1 causes oral herpes and a different form of the virus — herpes simplex virus 2 — causes genital herpes.)

How Are Mouth Lesions Diagnosed?

Your doctor or dentist can usually identify what kind of lesions or sores you have just by looking at your mouth. If you have recurrent, very large, or painful sores, you might need to undergo tests to make sure there’s not an underlying health problem.

For cold sores, your doctor may test your blood for antibodies to herpes, though this is not routinely done, as the test results can be misleading.

Make sure to contact your doctor if you’re experiencing a fever.

Treatment and Medication Options for Mouth Lesions

You can usually treat most common mouth sores or blisters yourself, at home, by taking a few simple steps or modifying certain behaviors.

Medication Options

Treatment for canker sores usually isn’t necessary and they typically clear on their own within a few days to a week.

Cold sores can also clear up on their own but antiviral medicine can speed up the process.

Nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin or ibuprofen, can help alleviate pain from both canker sores and cold sores. Medicated lip balms, especially those formulated for herpes 1 and canker sores, can also help.

For canker sores, an antiseptic mouthwash or a rinse containing the steroid dexamethasone can help ease pain and swelling. Lidocaine is another pain-reducing option.

Occasionally, a procedure known as cautery may be necessary, where the tissues of your mouth are burned and then sealed up by chemicals or another instrument.

Alternative and Complementary Therapies

Baking soda rinses might help to alleviate pain associated with mouth lesions. Applying ice, cold towels, or cooling ointments to afflicted areas may also soothe discomfort, as can applying small amounts of milk of magnesia on canker sores a few times a day.

Be sure to use a soft brush to brush your teeth. It’s thought that sodium lauryl sulfate, a common ingredient in toothpastes, could also trigger canker sores, so it might be a good idea to find a toothpaste without it if you have recurrent sores, and also discuss it with your dentist.

Duration of Mouth Lesions

As noted above, both canker sores and cold sores tend to go away on their own in a week or two. But complex canker sores last longer, may take several weeks to heal, and may cause scarring.

Always check with your doctor or dentist if you have unusually large or painful mouth lesions or sores that last longer than two weeks.

Prevention of Mouth Lesions

If you have cold sores, you should avoid kissing people when you have an outbreak — indeed, avoid close contact altogether. A person with a cold sore can spread the herpes virus through skin-to-skin contact with the sore, and also through their saliva. It’s also important to avoid contact with people who have weakened immune systems, such as newborns or people undergoing cancer treatment.

It’s never a good idea to share lip balms, razors, toothbrushes, towels, utensils, or beverages, but it’s especially important to avoid doing so if you have a cold sore or feel one coming on. And while it may be tempting to touch them, try not to. If you do, wash your hands.

When your lips are free and clear of sores, use a lip balm with sunscreen, as sunburn is another trigger for cold sores.

There’s no proven way to prevent canker sores, but following good oral hygiene, avoiding triggers, and managing stress can help. If you have recurring canker sores, your doctor may also suggest nutritional supplements if you consume low amounts of essential nutrients like folate, vitamin B6, vitamin B12, or zinc.

Complications of Mouth Lesions

Large, persistent, or unusually painful sores often need medical care.

Cold sores may spread to other parts of the body, especially in children, including fingertips, the eyes, and widespread regions of the skin. This may require antiviral treatment.

Research and Statistics: Who Has Mouth Lesions?

It’s been estimated that about 20 percent of Americans experience mouth lesions.

In the United States, the virus that causes cold sores (HSV-1) infects more than half the population by the time they’re in their twenties.

 According to the most recent data from the Centers for Disease Control and Prevention, about 48 percent of the general population has HSV-1, with women slightly more likely to have the virus than men (50.9 percent compared with 45.2 percent).

An estimated 3.8 billion people under the age of 50 worldwide have an HSV-1 infection.

Related Conditions and Causes of Mouth Lesions

Those with diseases of the immune system may be at risk of developing canker sores. These conditions include:

If you have recurrent oral lesions despite trying home remedies and waiting to see if they go away, it’s best to have a visit with your primary care doctor.

Common Questions & Answers

What causes lesions in your mouth?
Sores on the tongue or inside the mouth may be caused by infections, inflammation, or stress. Other causes include gritting your teeth, especially while sleeping, gum disease, cold sores, canker sores, and food allergies.
Sores tend to clear up on their own in a week or two. If you have recurrent, very large, or painful sores, you might need to undergo tests to make sure there’s not an underlying health problem.
Look for redness, shininess, or swelling in your mouth. If you see a red ring around a white or yellow center, it may be a canker sore. Cold sores will look like blisters filled with fluid.
Cold sores are caused by the herpes simplex virus. Recurrent canker sores may be due to rheumatologic conditions like lupus. Very rarely, mouth lesions may be caused by cancer. In general, mouth lesions aren’t a sign of a serious condition.
Mouth lesions often go away on their own. Canker sores and cold sores tend to clear up in a week or two. Check with your doctor or dentist, however, if you have large or painful sores that aren’t healing.

The Takeaway

  • Mouth sores such as cold sores and canker sores can be painful and bothersome but usually aren’t serious.
  • Cold sores are caused by the herpes virus and are contagious, while canker sores, which appear inside the mouth, are not.
  • To soothe discomfort, try rinsing your mouth with baking soda or apply small amounts of milk of magnesia on sore spots.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Plewa MC et al. Recurrent Aphthous Stomatitis. StatPearls. November 13, 2023.
  2. Canker Sore. Mayo Clinic. April 2, 2018.
  3. Cold Sore. Mayo Clinic. January 5, 2024.
  4. Cold Sores. Cleveland Clinic. September 4, 2024.
  5. Alli BY et al. Effect of Sodium Lauryl Sulfate on Recurrent Aphthous Stomatitis: A Systematic Review. Journal of Oral Pathology & Medicine. March 27, 2019.
  6. Cold Sore Remedies Dermatologists Recommend. American Academy of Dermatology. February 1, 2024.
  7. Randall D et al. Common Oral Lesions. American Family Physician. April 2022.
  8. Cold Sores. MedlinePlus. May 29, 2025.
  9. McQuillan G et al. Prevalence of Herpes Simplex Virus Type 1 and Type 2 in Persons Aged 14–49: United States, 2015–2016. Centers for Disease Control and Prevention. February 2018.
  10. Herpes Simplex Virus. World Health Organization. March 20, 2025.
  11. Canker Sores. Cleveland Clinic. June 9, 2022.
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Stacy A. Spizuoco, DDS

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Stacy Spizuoco, DDS, is a dentist in private practice in New York City. She is involved in charitable work, including organizing bi-annual dental missions with World of Smiles to Dominican Republic and volunteering at local missions such as Give Kids A Smile Day.

Dr. Spizuoco is 1 of 14 women dentists to be invited to the inaugural class of Glidewell Guiding Leaders Leadership program. She is a key opinion leader (KOL) for Glidewell Dental Lab and serves a consultant for Dental Advisors and for AEDIT. She has been published in Dental Economics and is a national lecturer and writer on various dental topics.

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