Birthmarks are colored marks on the skin that are present at birth or that develop shortly after birth, and may be brown, tan, black, blue or blue-gray, pink, white, red, or purple. Some birthmarks appear on the surface of the skin, some are raised above the surface of the skin, and some are located under the skin.

Most birthmarks need no treatment. They often fade as a child grows older. But some birthmarks may need treatment because of their location.

Experts do not know why some children have birthmarks and others do not.