Published: Jun 22, 2024

Mouth ulcers in children can be small but very painful.

Your child may cry when eating. They may refuse drinks. They may point to the tongue, cheek, gums, or lips. They may not want to brush their teeth.

Most mouth ulcers are not dangerous. Many heal on their own. But some need a doctor or dentist, especially if your child cannot drink, has a fever, has many sores, or the sore does not heal.

This guide explains the major causes of mouth ulcers in children, the 6 hidden triggers parents often miss, safe relief tips, what not to use, and when to seek care.

For more help, visit our First Aid & Home Remedies Hub, Nutrition & Vitamins Hub, Infections & Immune Health Hub, and Health Hub.

Medical note: This article is for education only. It does not diagnose or treat your child. Call a doctor, dentist, or urgent care if your child cannot drink, has signs of dehydration, has trouble breathing, looks very sick, has a high fever, has many sores, has a rash with fever, has ulcers that last more than 2 to 3 weeks, or has symptoms that feel serious.

Quick Answer: What Causes Mouth Ulcers in Children?

Mouth ulcers in children can be caused by mouth injury, cheek biting, braces, sharp teeth, viral infections, hand, foot, and mouth disease, stress, poor sleep, spicy or acidic foods, low iron, low vitamin B12, low folate, medicines, or health conditions.

The 6 hidden triggers parents often miss are:

1. Cheek or tongue biting
2. Braces, retainers, or sharp teeth
3. Viral illness, such as hand, foot, and mouth disease
4. Spicy, sour, or sharp foods
5. Stress, poor sleep, or tiredness
6. Low iron, vitamin B12, or folate

Most ulcers heal with gentle care. But repeated, severe, or long-lasting ulcers should be checked.

What do mouth ulcers look like in Children?

A mouth ulcer may look like a small sore inside the mouth.

It may be:

• White
• Yellow
• Gray
• Red around the edge
• Round or oval
• Flat or shallow
• Painful when touched

It may appear on the:

• Inner cheek
• Inner lip
• Tongue
• Gums
• Roof of the mouth
• Back of the throat

Your child may say their mouth burns, stings, or hurts.

Mouth Ulcer vs. Cold Sore vs. Hand, Foot, and Mouth Disease

Not all mouth sores are the same.

Canker sores are not the same as cold sores. Cold sores are often caused by a virus and can spread to others.

Trigger 1: Cheek or tongue biting

This is one of the most common causes.

A child may bite the inside of the cheek or tongue while eating, playing, falling, or sleeping.

The sore may appear after:

• A cheek bite
• A tongue bite
• A fall
• A sharp food scratch
• Rough tooth brushing
• A sports injury

The ulcer is often in one spot. It may match the bite area.

What helps?

• Use soft foods.
• Offer cool drinks.
• Avoid spicy foods.
• Use a soft toothbrush.
• Do not let the child pick at the sore.

If the same spot keeps getting sore, see a dentist.

Trigger 2: Braces, Retainers, Dentures, or sharp teeth

Dental rubbing can cause ulcers again and again.

This can happen from:

• Braces
• Retainers
• New dental work
• A sharp tooth
• A broken tooth
• A rough filling
• A loose baby tooth

The sore may be near the area that rubs.

What helps?

• Ask the dentist to check for sharp edges.
• Ask the orthodontist to adjust braces.
• Use orthodontic wax if advised.
• Keep the mouth clean.
• Use a soft toothbrush.

Do not ignore rubbing. It can stop the sore from healing.

Trigger 3: Hand, Foot, and Mouth Disease

Hand, foot, and mouth disease is common in young children.

It can cause painful mouth sores and a rash.

Signs may include:

• Fever
• Sore throat
• Painful mouth sores
• Drooling in young children
• Not wanting to eat
• Not wanting to drink
• Rash on hands
• Rash on feet
• Rash on buttocks or legs in some children

Most cases are mild, but mouth pain can make drinking hard.

What helps?

• Offer small sips often.
• Use cold drinks.
• Try popsicles or cold yogurt.
• Avoid citrus juice.
• Avoid spicy foods.
• Ask a doctor about safe pain medicine.
• Keep your child home if advised by local school or childcare rules.

Call a doctor if your child cannot drink, has signs of dehydration, has a stiff neck, is very sleepy, or looks very sick.

Trigger 4: Other Viral Infections

Other viruses can also cause mouth sores.

These may include:

• Cold viruses
• Flu-like illness
• Herpes virus
• Gingivostomatitis
• Throat infections

Some viral mouth sores come with fever, swollen gums, bad breath, drooling, or many painful sores.

What helps?

• Focus on fluids.
• Use soft foods.
• Ask about safe pain relief.
• Do not share cups or spoons.
• Wash hands often.
• Call a doctor if the fever is high or your child looks very sick.

Do not use antibiotics unless a doctor says they are needed. Many mouth sore illnesses are viral.

Trigger 5: Spicy, Sour, or sharp foods

Food can trigger or cause mouth ulcers in some children.

Common problem foods include:

• Chili
• Hot sauce
• Lemon
• Orange
• Pineapple
• Tomato sauce
• Vinegar foods
• Very salty snacks
• Hard chips
• Sharp toast

These foods can sting a sore and make eating worse.

What helps?

• Give soft foods.
• Offer mild foods.
• Skip citrus until healed.
• Skip spicy foods until healing.
• Keep a food diary if ulcers come back.

Do not remove many healthy foods for a long time without medical advice.

Trigger 6: Low Iron, Vitamin B12, or Folate

Some children with repeated mouth ulcers may have low iron, low vitamin B12, or low folate.

This does not mean every child with ulcers has a vitamin problem.

But it is worth asking if ulcers keep coming back.

Other signs may include:

• Tiredness
• Pale skin
• Poor appetite
• Dizziness
• Slow growth
• Sore tongue
• Cracks at the mouth corners
• Tingling in some cases

What helps?

• Ask the doctor if blood tests are needed.
• Do not give high-dose vitamins without advice.
• Offer iron-rich foods if suitable.
• Offer B12-rich foods if suitable.
• Ask for diet help if your child is picky or vegan.

For more food support, visit our Nutrition & Vitamins Hub.

Other Causes of Mouth Ulcers in Children

Some causes are less common but still important.

Stress and Poor Sleep

Some children get ulcers during school stress, exams, travel, poor sleep, or after illness.

Toothpaste Irritation

Some children are sensitive to strong toothpaste or mouthwash. Ask a dentist before changing your child’s dental routine.

Medicine Side Effects

Some medicines can cause mouth sores. Do not stop medicine without medical advice.

Food Allergy or Sensitivity

Some children react to certain foods. This is not always easy to prove. A diary can help.

Digestive or Immune Conditions

Repeated ulcers can sometimes be linked with celiac disease, inflammatory bowel disease, or immune conditions.

Oral Thrush

Thrush is a yeast infection. It may look like white patches, not just one ulcer. It is more common in babies, children using inhaled steroids, or children with low immunity.

Safe Relief for Mouth Ulcers in Children

There is no safe, instant cure for most mouth ulcers. The goal is to help your child drink, eat, sleep, and heal.

1. Give cold drinks

Cold drinks can soothe pain.

Try:

• Cold water
• Milk
• Cold smoothies without citrus
• Ice chips for older children
• Popsicles

Do not give ice chips to young children who may choke.

2. Offer soft foods

Soft foods hurt less.

Try:

• Yogurt
• Oatmeal
• Mashed potatoes
• Soft rice
• Soft pasta
• Scrambled eggs
• Soup that is warm, not hot
• Banana
• Avocado

3. Avoid foods that sting

Until the ulcer heals, avoid:

• Spicy foods
• Sour foods
• Citrus juice
• Tomato sauce
• Vinegar
• Very salty foods
• Hard chips
• Very hot drinks

4. Use a soft toothbrush

Keep brushing, but be gentle.

A dirty mouth can make pain worse. But hard brushing can make ulcers worse, too.

5. Ask about pain medicine

Ask your child’s doctor or pharmacist about the right dose of acetaminophen or ibuprofen for age and weight.

Do not give aspirin to children unless a doctor specifically says to.

6. Ask About Mouth Gels

Some gels may help with pain. But not all gels are safe for all ages.

Ask a doctor, dentist, or pharmacist before using numbing gels in young children.

Salt Water Rinse: Is It Safe for Children?

A warm saltwater rinse may help older children who can spit well.

Do not use it for toddlers or children who may swallow it.

How to use it for older children:

1. Mix half a teaspoon of salt in a cup of warm water.
2. Let your child swish gently.
3. Tell your child to spit it out.
4. Do not let your child swallow it.

It may sting for a moment. Stop if it upsets your child.

What Not to Use on Children’s Mouth Ulcers

Some home “cures” are too harsh for children.

Do not put these on a child’s mouth ulcer:

• Lemon juice
• Vinegar
• Undiluted hydrogen peroxide
• Aspirin tablets
• Alcohol
• Essential oils
• Hot salt
• Tooth whitening products
• Adult numbing gels without advice
• Harsh mouthwash

If it burns, it is not a good cure.

When to Call a Doctor or Dentist

Call a doctor or dentist if:

• Your child cannot drink well.
• Your child has no urine for 8 hours or more.
• Your child has dark urine.
• Your child has a very dry mouth.
• Your child has no tears when crying.
• Your child looks very sick.
• Your child has a high fever.
• Your child has many mouth sores.
• Your child has a rash on their hands or feet.
• Your child has swollen gums.
• Your child has ulcers that last more than 2 to 3 weeks.
• Ulcers keep coming back.
• The sore bleeds or grows.
• There is a lump in the neck.
• Your child has weight loss.
• Your child has trouble swallowing.

Seek urgent care for trouble breathing, severe sleepiness, stiff neck, confusion, dehydration, or symptoms that feel serious.

How Doctors Check Mouth Ulcers in Children

A doctor or dentist may:

• Look inside the mouth
• Check the tongue, cheeks, gums and throat
• Check for rash
• Ask about fever
• Ask if your child can drink
• Ask how long the sore has been there
• Ask if sores come back
• Check teeth, braces, or dental rubbing
• Ask about food and medicine
• Order blood tests if ulcers repeat
• Refer to a specialist if needed

Most children do not need many tests. Testing depends on symptoms.

How to Prevent Mouth Ulcers in Children

You cannot prevent every ulcer. But these steps can help.

• Use a soft toothbrush.
• Teach slow, gentle brushing.
• Fix sharp teeth or braces rubbing.
• Use orthodontic wax if advised.
• Offer a balanced diet.
• Help your child sleep well.
• Reduce stress when possible.
• Track food triggers.
• Avoid harsh mouthwash.
• Keep dental checkups.
• Teach handwashing to reduce viral spread.
• Do not share cups, spoons, or toothbrushes.

Foods That Help During a Mouth Ulcer

Food should be soft.

Good options include:

• Plain yogurt
• Milk
• Oatmeal
• Eggs
• Soft rice
• Soft pasta
• Mashed potato
• Soft chicken
• Soft fish
• Banana
• Avocado
• Warm soup
• Smoothies without citrus

Fluids are more important than solid food for a short time. Call a doctor if your child is not drinking.

Simple 7-Day Relief Plan for Parents

This is a comfort plan. It is not a cure for every cause.

Day 1: Check the Mouth

Look for one sore, many sores, gum swelling, throat sores, or a rash on hands and feet.

Day 2: Focus on Fluids

Offer small sips often. Use cold drinks if they help.

Day 3: Switch to Soft Foods

Use yogurt, oatmeal, eggs, soup, soft rice, and a banana.

Day 4: Remove Triggers

Stop spicy, sour, salty, sharp, and very hot foods until healing.

Day 5: Check Teeth and Braces

Look for rubbing, sharp edges, loose wires, or a tooth that cuts the cheek.

Day 6: Track Patterns

Write down sleep, stress, foods, fever, rash, and where the ulcers appear.

Day 7: Ask for Care if Needed

Call a doctor or dentist if the ulcer is not improving, keeps coming back, or your child is not drinking well.

FAQ

What causes mouth ulcers in children?

Common causes include cheek biting, tongue biting, hard brushing, braces, sharp teeth, viral illness, hand, foot, and mouth disease, spicy foods, acidic foods, stress, poor sleep, low iron, low vitamin B12, low folate, and some medicines.

Are mouth ulcers in children serious?

Most are not serious and heal on their own. But they can be serious if your child cannot drink, has dehydration signs, has a high fever, has many sores, or the ulcer lasts more than 2 to 3 weeks.

How long do mouth ulcers last in children?

Many mouth ulcers heal within 1 to 2 weeks. See a doctor or dentist if they last longer, keep coming back, or are very painful.

What is the fastest relief for mouth ulcers in children?

Fast relief may include cold drinks, soft foods, avoiding spicy and sour foods, using a soft toothbrush, and age-safe pain medicine if advised by a doctor or pharmacist.

Can hand, foot, and mouth disease cause mouth ulcers?

Yes. It can cause painful mouth sores, fever, sore throat, and a rash on the hands, feet, or other areas.

Can vitamin deficiency cause mouth ulcers in children?

Repeated ulcers may sometimes be linked with low iron, vitamin B12, or folate. A doctor can decide if blood tests are needed.

Can stress cause mouth ulcers in children?

Stress and poor sleep can trigger ulcers in some children. They are not the only causes, but they can be part of the pattern.

What foods should children avoid with mouth ulcers?

Avoid spicy foods, citrus, tomato sauce, vinegar, salty snacks, sharp chips, hard toast, and very hot drinks until the ulcer heals.

Should I use mouth gel for my child?

Ask a doctor, dentist, or pharmacist first. Some gels are not safe for all ages, especially young children.

When should I call a doctor?

Call a doctor if your child cannot drink, has no urine for 8 hours or more, has dark urine, has no tears, looks very sick, has a high fever, has many sores, has a rash, or the ulcer lasts more than 2 to 3 weeks.

Related Reading

• Mouth Ulcers: Causes, Fast Relief, Prevention, and When to Worry
• First Aid & Home Remedies Hub
• Nutrition & Vitamins Hub
• Infections & Immune Health Hub
• Digestive Health & Gut Hub
• Medical Tests & Screenings Hub
• Health Hub
• Healthy Lifestyle Roadmap: 14 Practical Tips for Better Health
• Effect of Unhealthy Lifestyle: Warning Signs, Health Risks, and How to Reset
• Health Screening 101: Simple Guide to Medical Tests

Key Takeaway

Mouth ulcers in children are common. Most heal on their own.

The most common causes include bites, braces, sharp teeth, viral illness, spicy or acidic foods, stress, poor sleep, and low nutrients.

The best home care is simple: cold drinks, soft foods, gentle brushing, fluids, and avoiding foods that sting.

Do not use harsh “cures” like lemon, vinegar, alcohol, aspirin, or essential oils on a child’s mouth sore.

Call a doctor if your child cannot drink, has dehydration signs, has high fever, has many sores, has a rash, looks very sick, or the ulcer does not heal.

Sources

• NHS — Mouth Ulcers
• HealthyChildren.org from the American Academy of Pediatrics — Mouth Ulcers or Sores
• Seattle Children’s — Mouth Ulcers
• CDC — About Hand, Foot, and Mouth Disease
• Nemours KidsHealth — Canker Sores
• Stanford Medicine Children’s Health — Canker Sores in Children
• NIDCR — Fever Blisters and Canker Sores
• Mayo Clinic — Canker Sore Symptoms and Causes

Adel Galal

Health & wellness writer with 30+ years of experience in nutrition, fitness, and healthy aging. Founder of NextFitLife.com — evidence-based health guidance.