Most birthmarks are harmless. But in rare cases, complications can occur that need to be treated.

Most birthmarks are harmless. But in rare cases, complications can occur that need to be treated.


Although it's rare, some haemangiomas can cause severe problems and can even be life-threatening. They need to be treated if they interfere with eating, breathing or eyesight.

If your child has a haemangioma near their eye, nose, mouth or nappy area, they may need to be referred to a specialist. Haemangiomas in these areas are more likely to become infected. If the birthmark bleeds, apply pressure to it until the bleeding stops.

See your GP if your child's haemangioma forms an ulcer. It may become infected and be very painful. Keep the wound clean and covered with a dressing. It should heal within two weeks.

Infected haemangiomas need urgent treatment with antibiotics. An infected ulcer may leave an unsightly scar.

If your child has more than five haemangiomas, they may also have internal haemangiomas. An ultrasound scan or magnetic resonance imaging (MRI) scan may be used to find out whether any internal haemangiomas are present. 

It's very unusual for internal haemangiomas to cause problems. But in rare cases they can cause coughing and difficulty breathing, which may indicate airway haemangiomas. Another possible symptom is blood in the stools, which may indicate a haemangioma in the bowel.

Capillary malformation (port wine stains)

Capillary malformation (port wine stains) can lead to the following complications:

  • glaucoma (raised pressure within the eye that affects vision) – this may develop if the birthmark affects both the upper and lower eyelids on the same side
  • Sturge-Weber syndrome – a rare disorder affecting the eyes and brain that's usually associated with a large port wine stain that extends across the forehead or scalp; find out more about Sturge-Weber syndrome on the NINDS website
  • soft tissue hypertrophy (the tissue beneath the birthmark enlarging) – this may occur on the lip, for example 
  • Klippel-Trenaunay syndrome – a rare disorder that's present at birth where the blood vessels fail to form properly; if your child has an enlarged port wine stain on their limb, they may have Klippel-Trenaunay syndrome; the NINDS website has more information about Klippel-Trenaunay syndrome 

All of the above conditions will need to be treated by a specialist.

Congenital melanocytic naevi

If a congenital melanocytic naevi increases in size or changes shape or colour, your doctor may recommend that you have a biopsy (where a tissue sample is taken so that it can be examined under a microscope).

You should see your doctor if you notice any of the following changes in your birthmark:

  • bleeding
  • inflammation (swelling)
  • itching
  • open sores
  • pain
  • changes in colour, size or texture

Although it's very rare, some congenital melanocytic naevi can develop into skin cancer. This risk increases with the size of the birthmark – the larger it is, the greater the risk.

Read more about moles.

Page last reviewed: 14/06/2016
Next review due: 14/06/2019