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Mouth ulcers in babies and children

Mouth ulcers are painful, clearly defined, round or oval sores that form in the mouth. There are different types of ulcer.

Types of ulcer

Canker sores (aphthous ulcer)

These are usually small and creamy-white and appear on the:

  • tongue
  • gums
  • lining of the mouth

They can be very painful and may prevent your child from eating and drinking. They often occur during times of stress.

Traumatic ulcer

A traumatic ulcer is larger and usually starts as a sore patch on the inside of the cheek. It can develop after an injury, possibly by biting or the rubbing of a rough tooth. It enlarges to form a painful yellow crater. It can take up to 14 days to heal.

Cold sore infection

A primary infection with the cold sore virus can result in white painful blisters:

  • on the roof of the mouth
  • on the gums
  • inside of the cheeks
Child with a mouth ulcer

Thrush infection

White curd-like blisters could be caused by a thrush infection.

Hand, foot and mouth disease

If your child has several ulcers in their mouth, this could be a sign of hand, foot and mouth disease.


Most ulcers will heal in their own time. This usually takes a week or two. You can give your child pain relief medicine such as children's paracetamol if they are in pain. Always follow the instructions on the packet.

Make sure your child is drinking enough fluids like water and milk. You can try offering them cold drinks through a straw if their mouth is very sore.

Offer them cool, soft foods to eat. Rough foods like toasts or cereal flakes might hurt their mouth.

Acidic fruits and fruit juices might sting their mouths too and are best avoided.

If you are bottle feeding your baby, make sure you are using the correct bottle teat. This will help to avoid any trauma to the inside of your baby’s mouth.

When to contact your GP

Contact your GP if the ulcers:

  • are very painful or red
  • look like white curds and won't wipe off - this is probably thrush
  • come back regularly

If the ulcers keep coming back, your GP may send your child for blood tests. This is to see if there is an underlying cause (such as being low in certain vitamins or iron, or coeliac disease).

Related topic

Thrush infection

page last reviewed: 17/05/2019
next review due: 17/05/2022