Hemangioma is a common type of birthmark. These birthmarks happen when many new blood vessels grow in a specific area on the skin. Blood vessels are tiny tubes that carry blood through the body. No one knows what causes blood vessels to group together. Most birthmarks don't hurt at all and they usually aren't a sign of any kind of illness. Lots of newborns have these birthmarks on their bodies, like between the eyebrows. These birthmarks usually disappear within the first few months to years of life. These birthmarks tend to disappear spontaneously. Most hemangiomas are not treated unless the hemangioma threatens the child's health, which occurs in about 1 in 3 children with hemagiomas.