Whereas pigmented birthmarks are caused by an excessive growth of the cells that pigment the skin, vascular birthmarks form when the blood vessels beneath the skin do not develop normally. Either they are too numerous or too large, and the result is a patch of skin that becomes deep red or purple.
There are three common types of vascular birthmarks:
Port wine stains
These birthmarks have been called port wine stains, as they resemble port wine in colour. Deep reddish purple patches can form, typically on the head, neck, arms or legs. They are not usually indicative of underlying health problems, but they are permanent, and can grow as the child grows. Their consistency can also change over time, making birthmark removal something to consider if the port wine stain is noticeable and likely to cause distress.
The most common type of vascular stain, these patches are lighter in colour than port wine stains, and usually appear on the eyelids, forehead, nose, lips or the back of the head or neck. They tend to fade with age, although not all of them do.
Also known as strawberry marks, these marks can be superficial or develop deeper within the skin. In the latter case, they take on a blue colour rather than the red of the superficial marks. They usually grow larger during the first six months of life and then start to shrink gradually, although not all do and need intervention.