Young woman with painful sore wondering what causes mouth sores

Mouth Sores: Common Causes, Remedies, and More

Medically reviewed by William Ross Perlman, PhD, CMPP on January 10, 2020. Written by Caitlin Boyd. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Mouth sores can appear as small lesions or cracks around the lips. In some cases, the sores can also develop inside the mouth. Mouth sores also commonly occur along the gums, lips, and lining of the cheeks.

Mouth sores aren’t always a purely cosmetic problem: in some cases, sores in your mouth could be a symptom of a serious health concern. So keep reading to find out the common causes of mouth sores, related health conditions, remedies, and more.

Common Causes of Mouth Sores


As the term implies, sexually transmitted infections (STIs) are infections that spread through sexual contact. Some STIs (like syphilis) can cause sores around your mouth or genitals. So if you notice an unexplained sore, consider testing with the at-home STD Test for women or men. Note that, while many STIs are treatable, early detection is key: if an STI goes untreated, it may result in serious health complications over time.

Canker Sores

Canker sores, also known as aphthous ulcers, often appear on your gums or inside of your mouth. These sores are not contagious. Instead, they often develop due to a minor injury.

If you develop frequent canker sores, you may have aphthous stomatitis. This chronic condition increases your risk of canker sores. While there is no cure, treatment can reduce your discomfort.

Some canker sores can be a sign of a nutritional deficiency. In particular, low B12 levels may trigger canker sores.

Fever Blisters

Fever blisters, also known as cold sores, are caused by the herpes simplex virus type 1 (HSV-1). This virus is very contagious. The virus often spreads through kissing, sharing eating utensils, or drinking from a shared glass. You can catch HSV-1 even if your partner has no visible sores.

People with HSV-1 can experience recurring outbreaks for the rest of their life. However, these outbreaks usually don't last long; most fever blisters heal within a few weeks and clear up on their own.

Over-the-counter products may help heal your fever blisters. If you have particularly stubborn fever blisters, your healthcare provider can also prescribe medication, or you can opt for a more convenient option of online cold sore medication.


Anemia develops when your body doesn’t have enough red blood cells that can effectively carry oxygen. People with anemia often develop sores or cracks around their mouths. Anemia can also cause fatigue, weakness, or dizziness.

Celiac Disease

Celiac disease causes an immune reaction when your body is exposed to gluten, a protein found in wheat and certain other foods. People with celiac disease often experience diarrhea, and abdominal pain.

Over time, celiac disease damages your small intestine. As a result, your body may not be able to absorb nutrients. Many people with celiac disease develop nutritional deficiencies, including low levels of B12. These deficiencies can increase the risk of mouth sores.


Syphilis is a bacterial infection that spreads through sexual contact. If you're infected with syphilis, you may develop ulcers around your mouth or genitals.

Syphilis can usually be cured with antibiotics. But if the infection is left untreated, you may develop life-threatening complications. To check for syphilis from the privacy of home, take the Everlywell at-home Syphilis Test (you’ll get to view your results on our secure, online platform). Read more about oral syphilis here.

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Seeking Medical Care for Mouth Sores

If you have a mouth sore, your healthcare provider can perform a visual exam. In some cases, a visual exam is all that's needed to make a diagnosis—but your provider may also ask about your other symptoms or medical history.

Once your provider determines what's causing your sore, they may suggest specific mouth sore treatments for you. If you have an infection, you may need antibiotics or antiviral medications, while nutritional deficiencies are often treated with dietary changes or nutritional supplements.

Other Remedies

Mouth sores often resolve on their own. While your sore is healing, avoid tobacco and excessive drinking, as these substances can irritate the sore and keep it from healing.

An over-the-counter mouth rinse can speed up the healing process. Rinsing your mouth with warm salt water several times a day also helps keep your sore clean and may allow it to heal faster.

Over-the-counter medications can sometimes clear up fever blisters and canker sores, so consider asking your healthcare provider or pharmacist which medication is right for you.

Common Questions About Mouth Sores

What Causes Mouth Sores?

There are several possible causes of mouth sores. Some mouth sores are a sign of an infection, while others may be a symptom of nutritional deficiency. Speaking with your healthcare provider is a great step to take to understand what’s causing the mouth sores you experience.

Are Mouth Sores Contagious?

Several health conditions can cause mouth sores. Some of these conditions (like sexually transmitted infections) are contagious, while others aren't. Your healthcare provider can determine whether you are at risk of spreading your sores to other people.

How Are Mouth Sores Treated?

Mouth sores caused by infections may need prescription medications. But if your canker sores are caused by a minor injury, they may heal on their own. If mouth sores develop because of a nutritional deficiency your healthcare provider may recommend dietary changes and/or nutritional supplements.

Mouth sores can be a sign of a sexually transmitted infection (STI), for example, or they may indicate a nutritional deficiency (such as low vitamin B12 levels). Check for STIs from the privacy of home with the Everlywell at-home STD Test for women or men.

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1. Sexually transmitted diseases (STDs). Mayo Clinic. URL. Accessed January 10, 2020.

2. Canker sore. Mayo Clinic. URL. Accessed January 10, 2020.

3. Stomatitis. Merck Manual. URL. Accessed January 10, 2020.

4. Canker Sores. Cleveland Clinic. URL. Accessed January 10, 2020.

5. Cold sore. Mayo Clinic. URL. Accessed January 10, 2020.

6. Anemia. Mayo Clinic. URL. Accessed January 10, 2020.

7. Celiac disease and gluten intolerance. URL. Accessed January 10, 2020.

7. Coeliac disease. NHS. URL. Accessed January 10, 2020.

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