Mouth Ulcers: Causes, Symptoms, and Treatment

Mouth ulcers are small, painful sores that form inside your mouth on the gums, tongue, inner cheeks, or lips. They are usually round or oval with a white or yellow center and red border. Most mouth ulcers heal on their own within one to two weeks. Common causes include minor injuries, stress, certain foods, or vitamin deficiencies. Treatment focuses on relieving pain and avoiding irritation. See a doctor if ulcers persist for more than three weeks or are unusually large.

In plain words

Mouth ulcers are painful sores inside your mouth. They are not the same as cold sores. They can appear on your gums, tongue, or inner cheeks. Most heal on their own in 1-2 weeks. Common causes include biting your cheek, stress, or eating certain foods. Some people get them more often than others. They can make eating and talking uncomfortable. You can treat them at home with salt water rinses or special gels. See a doctor if they last more than 3 weeks or are very large.

What is Mouth Ulcers: Causes, Symptoms, and Treatment?

Mouth ulcers are small, painful sores that form inside your mouth on the gums, tongue, inner cheeks, or lips. They are usually round or oval with a white or yellow center and red border. Most mouth ulcers heal on their own within one to two weeks. Common causes include minor injuries, stress, certain foods, or vitamin deficiencies. Treatment focuses on relieving pain and avoiding irritation. See a doctor if ulcers persist for more than three weeks or are unusually large.

Symptoms

Early symptoms

  • Round or oval sores inside the mouth: Ulcers typically appear as small, white or yellow lesions with a red border. They commonly form on the gums, tongue, inner cheeks, or lips. (1) (5)
  • Pain or discomfort: Ulcers can be painful, especially when eating, drinking, or talking. The pain may increase with irritation from acidic or spicy foods. (1)
  • Tingling or burning sensation: Some people notice a tingling or burning feeling in the area before an ulcer forms. This is often the first sign of an upcoming sore. (5)
  • Swelling around the sore: The tissue surrounding the ulcer may become swollen or inflamed, adding to the discomfort. (5)

Serious or emergency symptoms

  • Unusually large ulcers: Ulcers larger than 1 cm or those that spread rapidly may indicate a more serious condition and require medical attention. Consult a doctor or dentist. (6)
  • Ulcers lasting more than three weeks: Persistent ulcers that don’t heal after three weeks could be a sign of an underlying health issue, such as oral cancer or an autoimmune disorder. Seek medical evaluation. (6)
  • Fever or swollen lymph nodes: If ulcers are accompanied by fever, sluggishness, or swollen lymph nodes, it may indicate an infection or systemic condition. See a doctor promptly. (5)

Causes

Primary causes

  • Minor injuries: Accidental cheek bites, dental work, brushing too hard, or sharp foods like chips can damage the mouth lining and trigger ulcers. (2)
  • Stress or anxiety: Emotional stress or anxiety can weaken the immune system and make you more prone to developing mouth ulcers. (2)
  • Certain foods: Acidic or spicy foods, such as citrus fruits, chocolate, and coffee, can irritate the mouth and lead to ulcers in some people. (2)
  • Vitamin deficiencies: Low levels of iron, vitamin B12, or folate can contribute to recurrent mouth ulcers. (2)

Risk factors

Family history

If your family members experience frequent mouth ulcers, you may be more likely to develop them as well. (2)

Smoking cessation

Quitting smoking can temporarily increase the likelihood of mouth ulcers as the mouth adjusts to the change. (2)

Hormonal changes

Some women develop ulcers during menstruation due to hormonal fluctuations. (2)

Diagnosis

Mouth ulcers are typically diagnosed based on their appearance and your medical history. A doctor or dentist will examine the sores and ask about symptoms, triggers, and how long they’ve been present. If ulcers are unusually large, persistent, or accompanied by other symptoms, further tests may be needed to rule out underlying conditions such as infections, autoimmune disorders, or nutritional deficiencies.

Physical examination

To assess the size, location, and appearance of the ulcers. The doctor will also check for signs of infection or other oral issues. (6)

Medical history review

To identify potential triggers such as stress, dietary habits, or recent dental work. (6)

Blood tests

To check for nutritional deficiencies or signs of an underlying condition that could be causing recurrent ulcers. (6)

Treatment

Medication options

Topical corticosteroids

These reduce inflammation and pain, helping ulcers heal faster. They are available as pastes or mouth rinses. (3) (4)

Antiseptic mouthwashes

These help prevent infection and promote healing by reducing bacteria in the mouth. (3)

Pain-relieving gels

These provide temporary relief from pain and discomfort by numbing the affected area. (3)

Lifestyle and self-care

  • Avoid irritants: Steer clear of acidic, spicy, or rough foods that can aggravate ulcers. Opt for soft, bland foods until the sore heals. (3)
  • Maintain oral hygiene: Brush gently with a soft-bristled toothbrush and use a mild toothpaste. Avoid mouthwashes containing alcohol. (3)
  • Saltwater rinses: Mix a teaspoon of salt in a glass of warm water and rinse your mouth several times a day to soothe ulcers and promote healing. (4)
  • Manage stress: Since stress can trigger ulcers, practices like yoga, meditation, or deep breathing may help reduce their frequency. (3)

Always discuss dosing and treatment changes with your own prescriber.

Possible complications

  • Difficulty eating or drinking: Severe ulcers can make it painful to consume food or liquids, potentially leading to dehydration or malnutrition. (5)
  • Secondary infections: Open sores in the mouth can become infected with bacteria or fungi, requiring additional treatment. (5)
  • Psychological impact: Chronic or painful ulcers can affect self-esteem and cause anxiety, especially if they interfere with social interactions. (5)

When to see a doctor

Routine follow-up

  • If ulcers persist for more than three weeks without improvement, consult a doctor or dentist to rule out underlying conditions. (1)
  • Seek medical advice if ulcers are unusually large, frequent, or accompanied by other symptoms like fever or weight loss. (5)

Seek emergency care

  • Seek immediate care if ulcers are so severe that you're unable to eat or drink, risking dehydration or malnutrition. (5)

Frequently asked questions

How long do mouth ulcers last?

Most minor mouth ulcers heal on their own within 10-14 days without treatment. Larger or more severe ulcers may take up to six weeks to heal completely. If an ulcer persists beyond three weeks without improvement, it's advisable to consult a healthcare professional to rule out other conditions. (7)

Can mouth ulcers be a sign of cancer?

While most mouth ulcers are harmless, persistent ulcers that don't heal could rarely indicate oral cancer — especially if combined with other warning signs like unexplained numbness, loose teeth, or difficulty moving the jaw. Ulcers caused by cancer usually appear on or under the tongue but can form anywhere. Risk factors include tobacco use and heavy alcohol consumption. Any ulcer lasting more than three weeks warrants evaluation. (7)

Are mouth ulcers contagious?

No, common mouth ulcers (canker sores) are not contagious and cannot be spread through kissing, sharing utensils, or other close contact. This distinguishes them from cold sores (caused by the herpes simplex virus), which are contagious. If you're unsure which type of sore you have, look at the location: cold sores typically appear on the outer lip, while mouth ulcers form inside the mouth. (1)

What deficiency causes mouth ulcers?

Deficiencies in iron, vitamin B12, or folate (vitamin B9) are sometimes associated with recurring mouth ulcers. Some people find that increasing their intake of these nutrients reduces ulcer frequency. A simple blood test can check for these deficiencies. However, not everyone with mouth ulcers has a deficiency — other triggers like stress or food sensitivities are more common causes. (2)

How can I prevent mouth ulcers?

Preventive steps include maintaining good oral hygiene with a soft-bristled toothbrush, avoiding foods that irritate your mouth (common triggers include nuts, chips, spicy foods, and acidic fruits), managing stress through relaxation techniques, checking for and correcting any nutritional deficiencies (especially iron, B12, or folate), and avoiding toothpastes containing sodium lauryl sulfate if you suspect it's a trigger for you. (3)

References

  1. NHS — Mouth ulcers source 1
  2. NHS — Mouth ulcers - Causes source 2
  3. NHS — Mouth ulcers - Treatment source 3
  4. MedlinePlus — Canker sore source 4
  5. Mayo Clinic — Canker sore source 5
  6. Cleveland Clinic — Mouth Ulcers source 6
  7. MedlinePlus — Mouth disorders source 7