A port-wine stain is a birthmark. It is made of enlarged blood vessels. This makes the birthmark appear as a reddish-purple patch of skin. They can occur anywhere but are most common on the head and neck.

Port-wine stains are usually present at birth. They are often flat at first and raise up as the child ages. It may also get darker as the child grows. Other port-wine stains may develop at an older age, but this is rare. These types may occur after a traumatic injury.

Port-wine stains are generally harmless. They may cause emotional and social problems due to their visibility.

Port wine stains care caused by a problem with the small blood vessels in the skin. Blood vessels can normally open and close to meet the needs of the skin. In port wine stains, the blood vessels stay wide open. Blood fills the vessels causing the purple color and raised skin. It is not clear what causes the problems with the blood vessels.