What Are Mouth Lesions? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Sometimes it happens when you’re eating and, suddenly, you bite the side of your cheek. Or you notice a stinging and redness on your upper or lower lip and you know what’s coming: a cold sore. Or maybe you have a canker sore — one painful enough that it makes enjoying a meal difficult. You wouldn’t be alone.

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, aren't contagious. They develop on the tissues in the mouth or at the base of the gums, and they can be quite painful.

But 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.

Here’s what you need to know and what to do about these mostly harmless lesions.

A person with a mouth or tongue lesion may have lumps, bumps, little ulcers, or cuts inside or outside of their mouth and lips. The first thing to do is to identify the problem, since there are many different types of sores.

Use a bright light and a magnifying mirror to examine the inside of your mouth, even sticking out your tongue to check for lacerations or swelling on the top, bottom, and sides. You might want to check 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 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.

Cold sores are blisters filled with fluid. You can often feel a cold sore coming on before they show up. You’ll feel some tingling or burning in the area, or you might feel a sore throat.

Related: How Do I Know if I Have Herpes or Something Else?

Sores on the tongue or inside the mouth may also be caused or exacerbated by other infections, inflammation, stress, or, very rarely, cancer. If the sore is deep, or if it gets irritated or infected, it may also bleed.

Some mouth sores and lesions may have more obvious causes, such as sharp or broken teeth or braces with protruding wires.

Gritting or gnashing your teeth, especially while sleeping, can cause tiny bites on the inside of your cheeks. Gum disease and inflammation can also cause bleeding in and around the gumline.

Biting your tongue or chewing your lips can cause pain, swelling, and even small cuts. Drinking hot liquids, smoking cigarettes and cigars, and consuming alcoholic beverages can also lead to mouth lesions, as can brushing or flossing too vigorously or using a hard toothbrush.

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.)

While cold sores are caused by a virus, the exact cause of canker sores is unknown. But there are several things that can trigger an outbreak. These include food allergies, stress, hormonal changes, vitamin deficiencies, or even spicy foods. Acidic fruits and vegetables may also trigger canker sores.

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

Your doctor or dentist can 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, yet this is not routinely done as the test results can be misleading.

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

Prognosis of Mouth Lesions

Treatment isn't typically needed for sores, which tend to clear up on their own in a week or two.

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 canker sores or sores that don't seem to heal.

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

Medication Options

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

Depending on the type and size of the sore, or whether or not it is healing on its own, you may need antibiotics, an antiviral medication, an antiseptic mouthwash or a rinse containing the steroid dexamethasone to 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. 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.

Prevention of Mouth Lesions

It’s never a good idea to share lip balms, razors, toothbrushes, towels, 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, try not to touch them. If you do, wash your hands.

Related: Icky Mouth Mysteries Solved

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

• Lupus
• HIV
• Celiac disease
• Crohn’s disease

Deficiencies of the following nutrients may also lead to canker sores:

• Vitamin B12
• Vitamin B6
• Folate
• Iron
• Zinc

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.

The American Dental Association’s Mouth Healthy website is a trustworthy and thorough source of information about dental hygiene.