Spider nevus goes by several names: spider angioma nevus araneus vascular spider A spider nevus is a collection of small, dilated arterioles (blood vessels) clustered very close to the surface of the skin. The cluster of vessels is web-like, with a central spot and radiating vessels. Spider nevi (plural) can be caused by injuries, sun exposure, hormonal changes, or liver disease, but often the cause is unknown. For most people, the nevi are not a medical concern. In some cases, they cause discomfort. The vessel clusters can be treated or removed in a number of ways, which include the use of compression stockings, chemical injections, and laser treatments.