Spider veins are the mildest form of venous insufficiency. They are tangled groups of tiny blood vessels just under the skin's surface that resemble spider webs or tree branches. Typically, they are red, blue or purple and clearly visible on the thighs, lower legs and face. Spider veins can sometimes cover large areas of skin, but they are strictly a cosmetic problem, rarely causing physical symptoms.
Spider veins can be diagnosed by sight; some physicians prefer to conduct ultrasound exams to determine the extent of the problem and the underlying causes of the condition.
Risk factors for spider veins are similar to those for varicose veins: age, heredity, pregnancy, hormonal changes, obesity and extended periods of standing. Sun exposure and injuries to the skin's surface also can play a role in vein health. Some physicians believe that exercise, weight loss and the wearing of support hose and flat shoes instead of high heels can reduce the incidence of spider veins.