Mouth ulcers in babies
6-minute read
If your baby is younger than 3 months old and has a fever above 38°C, seek urgent medical attention or go to the nearest hospital emergency department.
Key facts
- Mouth ulcers are a type of sore that can develop in your baby's mouth, or on their lips, tongue and gums.
- If your baby has a mouth ulcer, they may feel some discomfort in their mouth, struggle to eat or drink, drool a lot or even develop a fever or rash on their body (if the ulcers are caused by a virus).
- There are many reasons why your baby can develop a mouth ulcer, such as herpes virus infection, hand, foot and mouth disease, fungal infections, deficiencies in some nutrients, an injury to their mouth, and sometimes the cause may be unknown.
- Your doctor will manage your baby’s mouth ulcers by treating the cause of the ulcer and recommending medicines to relieve pain.
- If the mouth ulcer is caused by a virus, your doctor may recommend that your baby stays home from child care until they have recovered, to prevent spreading the virus.
What are mouth ulcers?
Mouth ulcers are a type of sore. They can develop on your baby's mouth, lips, tongue and gums.
Mouth ulcers are also known as canker sores or aphthous ulcers.
Mouth ulcers are common in children. Different types of ulcers may look different, depending on what is causing them.
Most mouth ulcers get better on their own within 2 weeks. If an ulcer does not heal after 2 weeks, it is called a chronic ulcer.
What are the symptoms of mouth ulcers?
Your baby’s symptoms depend on what is causing their mouth ulcers. These may include:
- pain and discomfort in their mouth
- loss of appetite or difficulty feeding
- drooling more than usual
- redness and swelling inside their mouth
- being fussier than usual and difficult to settle
If your baby’s ulcer is caused by a virus, they may develop a fever or a rash on their skin.
If your baby is younger than 3 months old and has a fever above 38°C, seek urgent medical attention or go to the nearest hospital emergency department.
Read about how to tell if your child is sick.
What causes mouth ulcers?
There are many reasons why your baby might develop a mouth ulcer. These can include:
- viral infections, such as , hand, foot and mouth disease (caused by certain ) or cytomegalovirus (CMV)
- fungal infections
- nutritional deficiencies, including low levels of vitamin B, folic acid, iron or zinc
- side effects from some medicines, such as non-steroidal anti-inflammatory drugs (NSAIDs) and certain antibiotics
- injuries to the mouth, from falls, bumps, or accidentally biting their gums or lips
- other health conditions, such as , or
- sometimes ulcers may appear with no obvious cause
When should I see my doctor?
You should take your baby to their doctor if:
- your baby has mouth ulcers and you are worried about their health
- your baby is not drinking enough fluids (water, breastmilk or infant formula) and you are worried they might become dehydrated
- your baby is immunocompromised and has ulcers in their mouth
- you are worried your baby’s ulcer is becoming infected (it looks red, raised and filled with pus)
- it seems like your baby is in severe pain
How are mouth ulcers diagnosed?
Your baby's doctor can diagnose a mouth ulcer by examining their mouth and asking you about their symptoms and medical history. Sometimes the doctor may take a swab of your baby’s ulcer to send to the laboratory.
How are mouth ulcers treated?
Treatment for your baby’s ulcer includes treating the cause of their ulcer and their symptoms.
Treatment includes:
- hydration — make sure your baby drinks enough fluids, so they do not become dehydrated
- managing your baby’s pain — paracetamol, ibuprofen (if your baby is over 3 months of age) or numbing creams that relieve pain
- antiviral medicine if your baby’s ulcers are caused by the herpes simplex virus and they are immunocompromised
Try to encourage your baby to drink more fluids. If your baby is less than 6 months old, speak with your baby’s doctor about how to safely feed them fluids. Depending on their age, you may be able to offer them jelly, icy poles, oral rehydration solutions, water or milk.
Your baby’s doctor or pharmacist can explain which medicine is best for them and how to give it to your baby safely.
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What are the complications of mouth ulcers?
Complications from mouth ulcers are rare and can include:
- infection
- dehydration — if your baby is very dehydrated, they may need to go to hospital to receive fluids
If your baby has herpes simplex virus or hand, foot and mouth disease, they can develop very rare heart or neurological (nerve and brain) complications such as and .
Can mouth ulcers be prevented?
If your baby has mouth ulcers from a virus like herpes simplex and can’t control their saliva (dribbling), they should stay home from child care until they have recovered. This is to prevent spreading the virus to other children.
Resources and support
- Learn more about on The Royal Children’s Hospital Melbourne website.
- Read about at the National Health and Medical Research Council (NHMRC) website.
- Learn how to recognise and manage on the Sydney Children’s Health Network website.
- You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.
Looking for information for Aboriginal and/or Torres Strait Islander people?
The Government of Western Australia, Child and Adolescent Health Service has a for Aboriginal and/or Torres Strait Islander people.
Do you prefer to read in languages other than English?
The NSW Government Multicultural Health Communication Service has translated the resource into many community languages.
Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: May 2025
