Reviewed by Brian R. Robinson, MDSpider veins, also called telangiectasia, are tiny blue, red, or purple veins that often congregate on the thighs, ankles, and calves. They are visible on the surface of skin and can be caused by pregnancy, weight gain, and some medications.
When blood vessels just below the surface of the skin stretch and enlarge, they form bright reddish, purple, or blue spider-like formations. These formations usually occur on the legs, but can occur elsewhere on the body, in places including the face and torso.
Spider veins themselves are usually not particularly dangerous or painful, and many people develop a slight sprinkling of spider veins on their upper thighs, particularly as they age or during pregnancy in women. But some of the underlying causes may of spider veins are associated with serious pain, discomfort, and health risks.
Spider veins are the result of vascular insufficiency (insufficient function of the veins), and other, related forms of vascular insufficiency can include varicose veins, incompetent vein valves, congenital venous malformations (flaws in the veins or circulatory system that are present at birth).
