Why won't my mouth sore heal after three weeks?

Most mouth sores heal within one or two weeks. If yours has stuck around past three weeks, it's worth getting checked out. That doesn't automatically mean something serious. It's usually ongoing irritation, an infection or another health issue underneath. An exam gets you an answer and a plan for what to do next. 

What you will learn in this article: 

• Many common mouth sores heal within one or two weeks. 

• A mouth sore that has not healed after three weeks needs an exam. 

• Possible causes include irritation, infection, medicine and certain health conditions. 

• A lasting sore does not always mean cancer, but it should not be ignored. 

If your mouth sore has lasted longer than expected, schedule an appointment with an Aspen Dental provider. Your care team can examine it and help determine what is causing it. 

What counts as a mouth sore that won't heal? 

A mouth ulcer is an open sore inside your mouth. MedlinePlus recommends contacting a healthcare professional if a mouth ulcer has not gone away after three weeks.¹ 

Canker sores are painful white or yellow spots with a red edge that form inside the mouth. Cold sores are fluid-filled blisters that usually appear outside the mouth around the lips. The National Institute of Dental and Craniofacial Research (NIDCR) says both types usually clear within one or two weeks.² 

A sore that is still present after three weeks has lasted longer than expected. Even if it does not hurt much, it is time to have it examined. 

What causes a mouth sore that won't heal? 

Mouth sores can have many causes. According to MedlinePlus, irritation may come from biting your cheek, a sharp or broken tooth, braces, a burn or dentures that do not fit well. Infections, certain medicines and some health conditions can also cause sores.² 

The exact cause of canker sores is not known. NIDCR notes that possible triggers may include an injury, stress, low levels of folic acid, iron or vitamin B12, and conditions such as inflammatory bowel disease or celiac disease. Reports about these triggers vary.³ 

Soreness can also develop after dental work. A healing extraction, wisdom tooth or implant site is different from a typical mouth ulcer, but it should gradually improve. Contact your dental provider if the area is getting worse or has not improved after several weeks. 

Why do some sores take longer to heal? 

How long a sore lasts depends on what caused it. A sharp tooth, denture or orthodontic wire may keep rubbing the area. A sore linked to an infection, medicine or health condition may not improve until the underlying problem is addressed. 

Recent dental work can also leave an area sore while it heals. However, the area should slowly feel better. A sore that keeps getting irritated, becomes worse or remains after three weeks needs a professional exam. 

When should you see a dental provider about a mouth sore? 

A mouth sore that has lasted three weeks should be examined. NIDCR advises seeing a dental provider or doctor when a sore, irritation, lump or thick patch in the mouth lasts longer than two weeks.⁴ 

You should also get care if you notice: 

• A red or white patch 

• Unexplained bleeding 

• Numbness in your tongue, lip or mouth 

• A lump in your mouth or neck 

• Trouble chewing, swallowing or speaking 

• Trouble moving your jaw or tongue⁴

These signs can have many causes and do not automatically mean cancer. However, they should be checked instead of ignored. The bottom line is simple: do not keep waiting for a three-week-old sore to disappear. A sore that lasts, changes or repeatedly returns needs a professional look, even if it does not hurt. 

What happens at a dental evaluation for a mouth sore? 

Your dental provider will ask how long the sore has been there, whether it hurts and whether it has changed. They may also ask about recent injuries, dental work, medicines and other health symptoms. 

Next, your dental provider will examine the sore and the surrounding areas of your mouth. If something unusual is found, they may recommend additional testing or refer you to a doctor or specialist. 

Do not wait for a sore to go away on its own if it has already lasted several weeks. Contact your local dental provider to have it checked, discuss the next steps and find out what may be causing it. 

Why won't my mouth sore heal? FAQs 

Still have questions about a mouth sore that won't heal? These answers cover a few common concerns. 

Could a mouth sore that won't heal be linked to a nutritional deficiency or another health condition? 

Sometimes. Canker sores may be linked to low levels of folic acid, iron or vitamin B12. They may also occur with health conditions such as inflammatory bowel disease or celiac disease. If you get sores often, ask your doctor whether testing may help find the cause. 

What symptoms alongside a non-healing sore need faster attention? 

Tell your dental provider or doctor about unexplained bleeding, numbness, a hard lump, a red or white patch or trouble chewing or swallowing. Do not wait three weeks if these symptoms are already present. 

Should I see a dental provider or a doctor for a sore that won't heal? 

A dental provider is a good place to start for a sore inside your mouth. They can check for irritation from a tooth, denture or other dental problems. They can also refer you to a doctor or specialist if needed. 

Can I do anything at home while I wait to see a dental provider? 

Rinsing with salt water or cool water can ease irritation, and steering clear of hot, spicy, salty or acidic foods, including citrus, which can sting, helps too. Acetaminophen, taken as directed, may help with pain. These steps may bring relief, but they don't replace an exam once a sore has lasted three weeks. 

Does a mouth sore that won't heal always mean something serious? 

No. Many mouth sores are harmless and may come from simple irritation. However, some health conditions can first appear as a sore that does not heal. A dental provider or doctor needs to examine it to tell the difference. 

Sources 

¹ National Library of Medicine, MedlinePlus Medical Encyclopedia: “Mouth ulcers.” https://medlineplus.gov/ency/article/001448.htm 
² National Library of Medicine, MedlinePlus Medical Encyclopedia: "Mouth sores." https://medlineplus.gov/ency/article/003059.htm 

³ National Institute of Dental and Craniofacial Research: “Fever Blisters & Canker Sores.” https://www.nidcr.nih.gov/health-info/fever-blisters-canker-sores 

⁴ National Institute of Dental and Craniofacial Research: “Oral Cancer.” https://www.nidcr.nih.gov/health-info/oral-cancer