Birthmarks are abnormalities of the skin that are present when a baby is born. There are two types of birthmarks. Vascular birthmarks are made up of blood vessels that haven't formed correctly. They are usually red. Two types of vascular birthmarks are hemangiomas and port-wine stains. Pigmented birthmarks are made of a cluster of pigment cells which cause color in skin. They can be many different colors, from tan to brown, gray to black, or even blue. Moles can be birthmarks.
No one knows what causes many types of birthmarks, but some run in families. Your baby's doctor will look at the birthmark to see if it needs any treatment or if it should be watched. Pigmented birthmarks aren't usually treated, except for moles. Treatment for vascular birthmarks includes laser surgery.
Most birthmarks are not serious, and some go away on their own. Some stay the same or get worse as you get older. Usually birthmarks are only a concern for your appearance. But certain types can increase your risk of skin cancer. If your birthmark bleeds, hurts, itches, or becomes infected, call your health care provider.
References and abstracts from MEDLINE/PubMed (National Library of Medicine)