I have read that birthmarks are caused by abnormalities in the development of the blood vessels, but my question refers specifically to Haemangioma. They appear a few days after birth, the skin becomes quite raised and red, only to fade after a few years. I was wondering why they take a few days to appear and then fade? Why are they different from port wine stains which are flat and present from birth? Is there any reason why these marks are often on the face rather than other parts of the body?