Most birthmarks are harmless and may even go away on their own or shrink over time. Some birthmarks known as vascular birthmarks are caused by the presence of increased or abnormal blood vessels, resulting in redness on the skin. These vascular birthmarks include nevus simplex (salmon patch), infantile hemangioma (strawberry hemangioma), and port-wine stain. Treatment of birthmarks varies according to the type of birthmark presenting.