Mouth Ulcers: Causes, Symptoms, Treatment, Home Remedies and Prevention

A mouth ulcer can be surprisingly painful for something so small. A single sore on the inside of your cheek, lip or tongue can make eating, drinking, brushing your teeth or even talking uncomfortable.

The good news is that most mouth ulcers are harmless and heal on their own within 1–2 weeks. However, frequent, unusually large or persistent mouth ulcers may sometimes be linked to nutritional deficiencies, medications, infections or an underlying health condition. An ulcer that does not heal should not simply be ignored.

In this guide, we explain the causes of mouth ulcers, the best treatment options, natural ways to relieve them, foods to avoid, vitamin deficiencies associated with ulcers, how long they last and when you should see a doctor or dentist.

What Is a Mouth Ulcer?

A mouth ulcer is an open sore that develops on the soft tissues lining the inside of your mouth. It may occur on the inner cheek, inside the lips, tongue, gums, floor of the mouth or other areas of the oral cavity.

A typical canker sore is usually:

• Round or oval
• White, grey or yellowish in the centre
• Surrounded by a red border
• Painful or tender
• More uncomfortable when eating spicy, sour or salty foods

You may develop one ulcer at a time or several simultaneously.

One important point is that not every mouth sore is a canker sore. For example, cold sores caused by herpes simplex virus are different from typical aphthous mouth ulcers and are contagious.

What Are the Causes of Sores in the Mouth?

There is no single cause of mouth ulcers. Sometimes the reason is obvious, such as accidentally biting your cheek. In other cases, particularly recurrent mouth ulcers, there may be several contributing factors.

1. Accidental injury

Minor trauma is one of the most common reasons for a mouth ulcer.

You may develop an ulcer after:

• Biting your cheek or tongue
• Brushing too aggressively
• Eating hard or sharp foods
• Burning your mouth with hot food or drinks
• Having a sharp or broken tooth
• Dental treatment
• Wearing poorly fitting dentures
• Braces or orthodontic appliances rubbing against the cheek

Repeated irritation can prevent the damaged area from healing normally.

2. Stress and lack of sleep

Stress is a common trigger, particularly for people who already tend to develop recurrent aphthous ulcers.

Periods of emotional stress, anxiety, illness, exhaustion or inadequate sleep may coincide with the appearance of mouth ulcers. Stress does not necessarily mean it is the only cause, but it can contribute to flare-ups.

3. Vitamin and mineral deficiencies

Nutritional deficiencies can contribute to recurrent mouth ulcers.

The deficiencies most commonly associated with mouth ulcers include:

• Vitamin B12
• Folate (vitamin B9)
• Iron
• Sometimes other B vitamins and zinc

If ulcers keep returning, particularly when accompanied by tiredness, pale skin, changes in appetite or other symptoms, your doctor may consider blood tests to look for an underlying deficiency.

4. Food irritation and sensitivity

Certain foods can irritate an existing ulcer and make it much more painful. These include:

• Chillies and spicy foods
• Citrus fruits such as lemon and orange
• Pineapple
• Tomatoes
• Vinegar
• Very salty foods
• Very hot foods and drinks
• Hard or crunchy foods

Some people may also notice ulcers after eating particular foods because of an individual sensitivity.

5. Toothpaste or mouthwash

Some people find that toothpaste containing sodium lauryl sulphate (SLS) irritates their mouth or is associated with recurrent ulcers.

Strong or alcohol-containing mouthwashes may also irritate an already damaged area. If you notice that ulcers repeatedly occur after changing an oral-care product, discuss alternatives with your dentist.

6. Hormonal changes

Hormonal fluctuations may trigger mouth ulcers in some people. This can include periods around menstruation, pregnancy, puberty or menopause.

7. Certain medicines

Some medicines have been associated with mouth ulcers. These include certain non-steroidal anti-inflammatory drugs (NSAIDs), beta-blockers and other medications.

If you started developing recurrent ulcers after beginning a new medicine, do not stop the medicine on your own. Speak to your doctor about whether it could be contributing.

8. Infections and medical conditions

Multiple or recurrent mouth ulcers can sometimes occur alongside conditions such as:

• Viral infections
• Fungal infections
• Celiac disease
• Crohn’s disease and other inflammatory bowel diseases
• Oral lichen planus
• Behçet’s disease
• Certain autoimmune conditions
• Conditions affecting the immune system

This does not mean that having a mouth ulcer automatically indicates one of these diseases. Most ulcers are much simpler than that. The concern is greater when ulcers are recurrent, severe, persistent or accompanied by other symptoms.

What Is the Biggest Cause of Mouth Ulcers?

For an individual ulcer, minor injury or irritation is one of the most common causes—for example, biting the cheek, brushing too hard, rubbing from braces or a sharp tooth, or burning the mouth with hot food.

However, recurrent mouth ulcers often have no single identifiable cause. Stress, nutritional deficiencies, hormonal changes, certain foods, medications and underlying conditions may all play a role.

So, if you occasionally get one ulcer after accidentally biting your cheek, there may be little cause for concern. If you repeatedly develop ulcers without an obvious trigger, it is worth discussing the pattern with a healthcare professional.

What Vitamin Deficiency Causes Mouth Ulcers?

Vitamin B12 deficiency is one of the important nutritional deficiencies associated with recurrent mouth ulcers. Folate and iron deficiency are also well-established associations.

It is important not to assume that every mouth ulcer is caused by a vitamin deficiency. Taking supplements unnecessarily may not solve the problem if the actual cause is trauma, stress, medication or another condition.

If you regularly experience mouth ulcers, a doctor may recommend appropriate blood tests based on your symptoms and medical history. These may include tests for anaemia or iron deficiency and measurements of vitamin B12 and folate when clinically appropriate.

What Is the Best Medicine for Treating Mouth Ulcers?

There is no single medicine that is best for every mouth ulcer because treatment depends on its cause and severity.

For an uncomplicated ulcer, treatment is generally aimed at reducing pain, protecting the sore and allowing it to heal naturally.

A pharmacist or doctor may recommend:

• Pain-relieving gels, sprays or mouthwashes
• Protective oral gels
• Saline mouth rinses
• Appropriate antimicrobial mouthwash in selected cases
• Topical corticosteroid treatment for certain aphthous ulcers
• Treatment for an underlying nutritional deficiency when one is confirmed

Topical corticosteroids can be particularly useful for inflammatory aphthous ulcers, but they should be used appropriately and are not suitable for every type of mouth lesion.

Do not use leftover antibiotics or steroid medicines without medical advice. An ulcer caused by trauma, fungal infection, viral infection or another condition may require a completely different approach.

How Do I Heal a Mouth Ulcer?

Most ordinary mouth ulcers heal without specific treatment. Your goal should be to reduce irritation while your mouth repairs itself.

Try these steps:

Keep the area clean

Continue your normal oral hygiene routine, but be gentle around the ulcer.

Use a soft toothbrush

A soft-bristled toothbrush reduces the chance of further trauma.

Rinse with salt water

A simple saline rinse can soothe the mouth.

Mix approximately ½ teaspoon of salt in a glass of warm water, rinse your mouth and spit it out. Do not swallow the solution.

Drink plenty of fluids

Staying hydrated is especially important if the ulcer makes eating and drinking uncomfortable.

Choose soft foods

Foods that are cool, soft and easy to chew are usually more comfortable while the ulcer heals.

Avoid irritation

Temporarily avoid spicy, acidic, salty, very hot and crunchy foods.

Protect the ulcer from further injury

If a sharp tooth, broken filling, denture or braces is repeatedly rubbing the area, addressing that source of irritation can be an important part of healing.

What Kills Mouth Sores Fast?

There is no guaranteed way to kill or eliminate a typical mouth ulcer instantly.

Most mouth ulcers need time to heal. The NHS notes that there is no quick fix, although treatment can reduce pain and irritation and may help the healing process.

For faster symptom relief, a pharmacist or dentist may recommend a suitable topical pain-relieving product or medicated mouthwash. For some inflammatory aphthous ulcers, prescription topical corticosteroids may reduce inflammation and improve symptoms.

Be cautious about internet remedies that recommend putting harsh chemicals, concentrated antiseptics or other irritating substances directly onto an ulcer. Damaging the surrounding tissue can make the problem worse.

How to Stop Mouth Ulcers Naturally

If you prefer simple home measures, focus on reducing irritation rather than trying to “burn away” the ulcer.

Helpful measures include:

• Rinsing with warm salt water
• Drinking enough water
• Eating soft foods
• Avoiding spicy and acidic foods
• Avoiding very hot drinks
• Using a soft toothbrush
• Getting enough sleep
• Managing stress
• Avoiding picking or touching the ulcer
• Maintaining good oral hygiene

Honey is sometimes used as a home remedy for mouth sores, but it should not be considered a guaranteed cure. Natural remedies may provide comfort, but persistent or recurrent ulcers still need appropriate evaluation.

Can Curd Cure Mouth Ulcers?

Curd does not cure mouth ulcers.

However, plain, unsweetened curd may be comfortable to eat because it is soft and relatively mild. Its texture can make it easier to consume when chewing is painful.

If curd feels soothing, there is generally no reason to avoid it unless dairy products irritate you or you have another reason to restrict them.

The important distinction is that curd may be a comforting food, but it does not treat the underlying cause of a recurrent mouth ulcer or replace appropriate treatment for a vitamin deficiency, infection or other condition.

Can I Brush My Teeth With a Mouth Ulcer?

Yes. You should continue brushing your teeth when you have a mouth ulcer.

Stopping oral hygiene completely can allow plaque and bacteria to build up and may make your mouth less healthy.

Instead:

• Use a soft-bristled toothbrush.
• Brush gently.
• Avoid aggressively scrubbing the ulcer.
• Take care around painful areas.
• Consider an SLS-free toothpaste if you frequently experience ulcers and suspect your toothpaste is irritating your mouth.

If brushing is extremely painful, speak with a dentist or pharmacist about ways to manage the discomfort while maintaining oral hygiene.

Is It Safe to Kiss With Mouth Ulcers?

It depends on what type of sore you have.

A typical aphthous ulcer or canker sore inside the mouth is not contagious, so it cannot normally be passed to another person through kissing.

However, cold sores are different. Cold sores are usually associated with herpes simplex virus and are contagious, particularly when active lesions or blisters are present.

If you are unsure whether the lesion is a canker sore or a cold sore, it is safer to avoid kissing or oral contact until the lesion has been assessed or healed.

How Long Do Mouth Ulcers Last?

Most uncomplicated mouth ulcers heal within 7–14 days. Some sources describe typical aphthous ulcers as healing in around 7–10 days, while the NHS advises that common ulcers generally clear within a week or two.

The exact duration can depend on:

• The size of the ulcer
• Its location
• Whether it is repeatedly irritated
• Your general health
• Whether there is an underlying nutritional deficiency or medical condition
• Whether it is actually a mouth ulcer or another type of lesion

When should you worry about a mouth ulcer?

You should arrange an evaluation with a doctor or dentist if:

• The ulcer lasts longer than 2–3 weeks
• It keeps coming back frequently
• It is unusually large
• It becomes increasingly painful
• It bleeds
• It becomes hard or develops an unusual appearance
• You have difficulty eating, drinking, swallowing or speaking
• You develop unexplained weight loss
• You have persistent diarrhoea or abdominal symptoms
• You develop joint pain or skin lesions along with the ulcers
• You notice a lump or persistent red or white patch in the mouth

A persistent mouth ulcer does not necessarily mean cancer, but a non-healing oral ulcer should be examined because, in uncommon cases, persistent oral lesions can be associated with oral cancer.

This is particularly important for people who use tobacco or regularly consume alcohol, as these are important risk factors for oral cancer.

How Are Recurrent Mouth Ulcers Diagnosed?

A doctor or dentist will usually begin by examining the mouth and asking questions about:

• How often the ulcers occur
• How long they last
• Where they appear
• Whether they are painful
• Your diet
• Medications
• Stress and lifestyle factors
• Recent dental treatment or injury
• Other symptoms

If the ulcers are recurrent, severe or persistent, further investigation may sometimes be appropriate.

Depending on the situation, a doctor may consider blood tests such as a complete blood count, iron studies, vitamin B12 or folate testing. Additional investigations may be considered if symptoms suggest an underlying gastrointestinal, inflammatory or immune-related condition.

The purpose of testing is not simply to find a vitamin deficiency. It is to understand why the ulcers keep occurring and address the underlying problem where possible.

How to Avoid Getting Mouth Ulcers

You cannot prevent every mouth ulcer, particularly if you are prone to recurrent aphthous ulcers. However, several habits may reduce your risk.

Practise gentle oral hygiene

Brush twice a day with a soft toothbrush and avoid brushing aggressively.

Protect your mouth from injury

Be careful when eating hard foods and address sharp teeth, broken fillings or poorly fitting dental appliances.

Identify food triggers

If particular foods consistently trigger or worsen your ulcers, reduce or avoid them.

Eat a balanced diet

A varied diet containing adequate iron, folate, vitamin B12 and other nutrients can help prevent nutritional deficiencies.

Manage stress

Regular sleep, physical activity, relaxation techniques and healthy stress-management habits may help if stress is one of your triggers.

Stay hydrated

Adequate fluid intake helps maintain normal oral comfort and makes it easier to cope with an ulcer when one occurs.

Have regular dental check-ups

A dentist can identify sharp teeth, broken fillings, braces or other sources of repeated irritation.

Mouth Ulcer vs Cold Sore: What Is the Difference?

This is a common source of confusion.

A healthcare professional can help distinguish between different types of oral lesions when the appearance is unclear.

Frequently Asked Questions About Mouth Ulcers

What are the causes of sores in the mouth?

Common causes include accidental biting, trauma from braces or sharp teeth, aggressive brushing, burns from hot food, stress, food irritation, hormonal changes, certain medicines and nutritional deficiencies such as vitamin B12, folate and iron deficiency. Recurrent ulcers can occasionally be associated with infections or underlying medical conditions.

What is the best medicine for treating mouth ulcers?

There is no single best medicine for every ulcer. Pain-relieving gels or mouthwashes can help with symptoms, while topical corticosteroids may be prescribed for some aphthous ulcers. Treatment should depend on the type and cause of the lesion.

How do I heal a mouth ulcer?

Keep the mouth clean, brush gently with a soft toothbrush, drink enough fluids, use a warm salt-water rinse and avoid spicy, acidic, salty, very hot and crunchy foods until the ulcer heals.

What kills mouth sores fast?

There is no instant cure for an ordinary mouth ulcer. Pain-relieving topical products can make the sore more comfortable, while appropriate treatment may shorten symptoms in some cases. Most ulcers heal naturally within one to two weeks.

Is it safe to kiss with mouth ulcers?

Typical canker sores inside the mouth are not contagious. However, cold sores caused by herpes simplex virus are contagious. If you are unsure what type of sore you have, avoid kissing until the lesion has healed or been assessed.

Can curd cure mouth ulcers?

No. Curd may be a soft, comfortable food when your mouth is sore, but there is no reason to consider it a cure. Recurrent ulcers require attention to their underlying cause.

What vitamin deficiency causes mouth ulcers?

Vitamin B12, folate and iron deficiencies are among the nutritional deficiencies associated with recurrent mouth ulcers. If ulcers frequently return, appropriate blood testing may be recommended.

How long do mouth ulcers last?

Most ordinary mouth ulcers heal within 7–14 days. An ulcer lasting longer than two to three weeks should be assessed by a doctor or dentist.

How can I stop mouth ulcers naturally?

Salt-water rinses, good oral hygiene, adequate hydration, soft foods, avoiding irritating foods and managing stress can help relieve symptoms. These measures do not necessarily prevent every recurrence.

Can I brush my teeth with a mouth ulcer?

Yes. Continue brushing, but use a soft toothbrush and be gentle around the ulcer. Maintaining oral hygiene is important while the sore heals.

What is the biggest cause of mouth ulcers?

Minor trauma or irritation is one of the most common causes of an individual mouth ulcer. Recurrent ulcers, however, can have several triggers and sometimes no identifiable cause.

When Should You See a Doctor or Dentist for a Mouth Ulcer?

A mouth ulcer that appears occasionally and disappears within a week or two is usually not a cause for concern.

However, do not ignore a mouth ulcer that refuses to heal.

Seek professional advice if an ulcer persists for more than two to three weeks, repeatedly returns, is unusually large, bleeds, becomes increasingly painful or occurs along with other unexplained symptoms. Persistent oral lesions sometimes require further examination or investigation to rule out nutritional deficiencies, inflammatory conditions, infections and, rarely, oral cancer.

The most important message is simple: most mouth ulcers are temporary, but a mouth ulcer that does not heal deserves attention.

To consult a Doctor at Sparsh Diagnostic Centre, call our helpline number 9830117733.

 

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Medically Reviewed By

This article has been medically reviewed by Dr. Jaydeep Roy, BDS, Dental Surgeon at Sparsh Diagnostic Centre.

The content has been reviewed for medical accuracy, clinical relevance and clarity to ensure that the information about root canal treatment, its procedure, recovery, benefits and potential risks is consistent with current dental practice and patient-care guidance.

Medical Reviewer: Dr. Jaydeep Roy, BDS
Speciality: Dentistry
Medical Review Date: 3rd September 2026

This article is intended for general health information and educational purposes only. It should not be used as a substitute for professional dental advice, diagnosis or treatment.

 

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No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.