Mouth ulcers, which include canker sores, are small sores that develop within the mouth. There are no definite causes of mouth ulcers, but some injuries, allergies, or sensitivities may trigger them.
Mouth ulcers are painful and typically small lesions that develop in your mouth or at the base of your gums. They can make eating, drinking, and talking uncomfortable.
Types of mouth ulcers include canker sores and the sores caused by hand, foot, and mouth disease.
Mouth ulcers are rarely contagious and usually go away after 1 to 2 weeks, even without treatment. If you get a mouth ulcer that is large, is extremely painful, or lasts for a long time without healing, seek the advice of a doctor or dentist.
There’s no definite cause behind mouth ulcers, but certain risk factors and triggers have been identified.
People assigned female at birth, children, adolescents, and those with a family history of mouth ulcers have a higher risk of developing them.
- minor mouth injury from dental work, hard brushing, sports injury, or an accidental bite
- dental braces
- toothpaste or mouthwash that contains sodium lauryl sulfate (SLS)
- an allergic response to oral bacteria
- bacterial, viral, or fungal infections in the mouth, such as hand, foot, and mouth disease
- sensitivities to acidic foods and beverages like strawberries, citrus fruits, pineapple, chocolate, and coffee
- certain nutrient deficiencies, especially vitamin B9 (folate), vitamin B12, zinc, and iron
- hormonal changes, such as those that occur during menstruation or pregnancy
- emotional stress
- lack of sleep
Mouth ulcers can also be a sign of conditions that are more serious and require medical treatment, such as:
- celiac disease
- inflammatory bowel disease (IBD), including ulcerative colitis
- some autoimmune diseases, including:
- Behçet’s disease, a rare condition that causes inflammation throughout the blood vessels
Symptoms of mouth ulcers may vary depending on their cause, but they typically include:
- painful sores that may be yellow, white, or red
- sores on the inside of the mouth, such as on your tongue or the insides of your cheeks or lips
- areas of redness surrounding the sores
- pain that worsens when you eat, drink, or talk
You may have more than one mouth ulcer at the same time.
Mouth ulcers are not usually contagious unless they’re caused by an infection such as hand, foot, and mouth disease.
Canker sores are the most common type of mouth ulcer, with 20% of people having a canker sore at least once. There are three main types of canker sores:
Minor canker sore
Minor canker sores are small oval or round ulcers measuring under 5 millimeters (mm). They heal within 1 to 2 weeks and don’t cause scars.
According to DermNet New Zealand, 80% of people with canker sores have minor canker sores, making them the most common type.
Major canker sore
Major canker sores are larger and deeper than minor ones. They often measure over 10 mm.
They have irregular edges and can take weeks or months to heal. Major canker sores can result in long-term scarring.
Herpetiform canker sore
Herpetiform canker sores are pinpoint-sized, occur in clusters, and often appear on the tongue. Sometimes the clusters can merge to form one large sore.
Herpetiform canker sores have irregular edges and often heal, without scarring, within 1 month.
They’re called “herpetiform” because they may resemble the sores caused by herpes. Herpetiform canker sores are not otherwise associated with herpes infection.
When to see a doctor or dentist
See a doctor or dentist about your mouth ulcers if you develop any of the following:
- unusually large mouth ulcers
- new mouth ulcers that appear before the old ones heal
- sores that persist for more than 3 weeks
- painless sores
- sores that extend to the lips
- pain that you’re unable to manage with over-the-counter or natural medications
- severe problems eating and drinking
- high fever or diarrhea whenever your mouth ulcers appear
Your doctor will be able to diagnose mouth ulcers through a visual exam. You might be tested for other medical conditions if you have frequent, severe mouth ulcers.
A cold sore is another common type of oral lesion. Although mouth ulcers and cold sores share some causes and symptoms, it’s usually easy to tell the two apart.
Mouth ulcers only appear inside the mouth.
Although cold sores can appear inside the mouth, they mainly appear right above, below, or on your lips. They may also spread to the nose or chin. Cold sores are also fluid-filled, making them a type of blister.
Most mouth ulcers are not contagious. Cold sores are typically caused by the herpes virus and are always contagious.
Cold sores are also more likely to cause additional symptoms beyond the lesions, including:
- swollen lymph nodes in the neck
Both types of lesions can cause a burning or tingling sensation on the skin that may start a few days before the lesions appear. However, this sensation is more closely associated with cold sores.
Aphthous ulcer is another name for a canker sore. The medical term “aphtha” has a few definitions but is mostly used to refer to a small ulcer.
Most mouth ulcers don’t need treatment.
However, if you get mouth ulcers often or they’re extremely painful, a number of treatments and home remedies can decrease pain and healing time. These include:
- covering the ulcer with a paste made from baking soda
- using other topical pastes
- placing milk of magnesia on the ulcer
- using a mouth rinse made from salt water and baking soda
- using a mouth rinse that contains a steroid to reduce pain and swelling
- applying ice to the ulcer
- placing a damp tea bag on the ulcer
- taking supplements if you have deficiencies in certain nutrients, including vitamin B9 (folate), vitamin B12, zinc, and iron
- using over-the-counter topical products that are made with benzocaine, like Orajel and Anbesol
- trying natural remedies, such as echinacea, myrrh, and licorice root (may come in various forms, like teas or oils)
You can take these steps to help reduce the occurrence of mouth ulcers:
- Avoid foods that irritate your mouth. That includes acidic fruits, nuts, chips, and anything spicy. Instead, choose whole grains and nonacidic fruits and vegetables. Eat a well-balanced diet and consider taking a daily multivitamin.
- Try to avoid talking while you’re chewing your food to reduce accidental bites.
- Reduce your stress.
- Maintain good oral hygiene by flossing daily and brushing after meals.
- Avoid hard-bristled toothbrushes and mouthwashes containing sodium lauryl sulfate (SLS) or alcohol.
- Ask your dentist to give you wax to cover dental or orthodontic mouth devices that have sharp edges.
- Get adequate sleep and rest. This will not only prevent mouth ulcers but a host of other illnesses as well.