Mouth Ulcers: Causes, Symptoms & Treatment

If you have a small, painful sore in your mouth, it may be a mouth ulcer. Also known as canker sores or aphthous ulcers, mouth ulcers commonly appear as shallow lesions inside your mouth.

Unlike cold sores, most mouth ulcers aren’t contagious, and they usually go away on their own within two weeks. Home treatments can relieve mouth pain while the ulcer heals.

Call your doctor or dentist if you have a mouth ulcer or cluster of sores that are unusually large, extremely painful, or last longer than three weeks. A mouth sore that doesn’t go away or grows larger may be a sign of oral cancer.¹

What Does a Mouth Ulcer Look Like?

Mouth ulcers look like round or oval sores on the soft tissues inside your mouth. They usually appear on the lips or cheeks but can also develop:

• On the sides of the tongue
• Beneath the tongue
• Around the gums
• On the upper palate

A mouth ulcer can be white, yellow, grey, or red and may appear swollen. You can have a single ulcer or many, and they’re typically small and shallow.

Three types of mouth ulcers are categorized by size and how long they last:

1. Minor aphthous ulcers. These are smaller than 5 mm and heal within 7 to 14 days. 80% of mouth ulcers are minor.⁸
2. Major aphthous ulcers. These are larger than 5 mm and heal slowly over several weeks or months. Major ulcers often cause scarring.

Herpetiform ulcers. Multiple ulcers that appear as a cluster of 10 to 100 pinpoints and usually heal within one month.

Symptoms of Mouth Ulcers

The primary symptom of a mouth ulcer is the appearance of a small sore inside your mouth. Other symptoms can include:

• Pain that worsens when eating spicy, sour, or salty foods
• Loss of appetite due to mouth pain
• Discomfort while brushing your teeth
• Swelling around the sore

Mouth ulcer symptoms may worsen during periods of stress, illness, or lack of sleep. 

What Causes Mouth Ulcers?

Although mouth ulcers are common, the exact cause remains unknown. Factors contributing to mouth ulcers include:

• Minor oral tissue trauma. Examples include accidentally biting the inside of the cheek, sharp edges on dental appliances or teeth, or sports injuries.
• Food sensitivities. Coffee, chocolate, eggs, nuts, and spicy or acidic foods are common culprits.
• Nutritional deficiencies. Not getting enough iron, folate (folic acid), zinc, or vitamin B-12 may increase the risk of mouth ulcers.
• Sodium lauryl sulfate. Some toothpastes and mouth rinses contain this ingredient.
• Allergies. Certain bacteria can cause an allergic reaction in your mouth.
• Hormonal changes. These often occur during puberty, pregnancy, and menopause.
• Health conditions. Mouth ulcers are linked to medical conditions like diabetes, inflammatory bowel disease, and immune disorders.

Stress and smoking can make you more prone to developing mouth ulcers.

What is the Difference Between a Mouth Ulcer and Cold Sore?

Canker sores and cold sores are not the same.

• Mouth ulcers. These sores appear inside your mouth. They’re caused by various factors like vitamin deficiency, injury, and irritation.
• Cold sores. These blisters appear on your lips or around the mouth. They’re caused by a virus and are contagious.

When to See a Doctor for a Mouth Ulcer

See a doctor or dentist if you experience any of the following:

• Canker sores that last three weeks or more. Mouth ulcers typically last one to two weeks. If they last longer than this, see a doctor.
• Unusual sores. If you are used to getting canker sores repeatedly, you know what typical sores look like. If you notice a different type developing in your mouth, take extra caution.
• Sores that spread rapidly. This may be a sign of oral cancer.
• Extremely large or painful sores. Severe pain or unusually large sores can signify a more serious condition.
• A fever accompanies them. Mouth ulcers are not usually accompanied by a fever, so if they are, consider medical attention.
• Bad breath. The bad breath may be caused by food debris that remains in your mouth for a long time. If you leave this untreated for a long time, an infection can develop.

How are Mouth Ulcers Diagnosed?

A mouth ulcer is diagnosed through a simple visual exam. However, further tests may be needed if you have other worrisome symptoms.

If your oral health expert cannot identify the origin of your mouth ulcers, or if the ulcers do not respond to standard treatments, you may need a biopsy of the ulcer and some surrounding tissue. 

A biopsy is a process that involves the removal of a tissue sample for examination under a microscope and diagnosis.

Mouth Ulcer Treatment

The best way to get rid of a mouth ulcer depends on the underlying cause.

Depending on your needs, mouth ulcer treatment may include:

Avoiding Certain Foods

Foods that can irritate a mouth ulcer include:

• Crispy or crunchy foods
• Acidic, salty, and spicy foods
• Carbonated drinks
• Alcohol

Focus on eating soft foods and soups while a mouth ulcer is healing. Be sure to let hot food cool down a bit before eating.

Changing Oral Hygiene Products

Brushing your teeth with a mouth ulcer can be uncomfortable, but it’s important to maintain good oral health. Using a soft toothbrush can prevent mouth injuries that may increase the risk of new sores developing.

Check your toothpaste and mouthwash ingredients, and avoid irritants like alcohol and sodium lauryl sulfate. 

Herbal Remedies

Plant-based remedies used as mouth ulcer treatment include:⁷

• Aloe vera
• Guava
• Papaya
• Capsicum
• Turmeric
• Licorice (the root, not the candy)
• Myrrh
• Rhubarb
• Echinacea

Nutritional Supplements

If a mouth ulcer is caused by a nutritional deficiency, taking supplements may help. These may include:

• Vitamin B9 (folate)
• Vitamin B12
• Iron
• Zinc

Medications

Over-the-counter medications can relieve the pain and symptoms of mouth ulcers, including:

• Topical ointments that contain benzocaine or lidocaine
• Nonsteroidal anti-inflammatory drugs (NSAIDs) like diclofenac
• Antimicrobial mouthwash

Home Care

Other home care techniques for mouth ulcer treatment include:

• Putting ice on the ulcer
• Placing a wet tea bag on the ulcer
• Applying milk of magnesia to the ulcer
• Coating the ulcer with a baking soda paste

Professional Medical Treatment

If your mouth ulcer is severe or persists despite home care, your doctor or dentist can recommend the best treatment for you.

Treatment might be as easy as smoothening a sharp tooth poking your cheek. Other times, your doctor may recommend steroids, laser treatment, or cauterization (burning).

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Mouth Ulcers: Causes, Symptoms & Treatment

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Tips for Preventing Mouth Ulcers

There are things you can do to reduce the recurrence of mouth ulcers:

• Avoid food irritants. This may include acidic fruits, coffee, spicy foods, and chips.
• Eat healthy foods. A healthy diet includes whole grains, veggies, lean protein, and nonacidic fruits. Consider taking a vitamin supplement to fill in nutritional gaps.
• Chew carefully. This will help you avoid accidental cheek bites.
• Maintain good oral hygiene. Use a soft-bristled toothbrush and floss to clean your teeth at least twice daily. Avoid products with alcohol or sodium lauryl sulfate.
• Reduce stress. Relaxation techniques like yoga, meditation, and breathwork are great options for managing stress.
• Get enough sleep. Proper sleep is fundamental for overall health, including preventing mouth ulcers.
• Talk to your dentist about mouth pain. Dentures and orthodontic appliances that poke your mouth can cause sores.

Some types of prescription medications, such as antidepressants, can also cause mouth ulcers.⁵ If your prescribed medication is causing sores in your mouth, consult your doctor for other options.

Summary

Mouth ulcers look like small, round, or oval sores inside your mouth. Also known as aphthous ulcers or canker sores, mouth ulcers are common and usually heal on their own within two weeks.

Call your doctor or dentist if a mouth ulcer doesn’t go away after three weeks or if it’s extremely large or painful. Most mouth ulcers respond to home treatment, like avoiding irritating foods, updating your oral hygiene routine, and using over-the-counter products.

Professional medical treatment for mouth ulcers includes steroids, laser treatment, and cauterization.