"Spider vein" is the common term for venous telangectasias, the condition of visible veins that may appear at the surface of the leg, pelvis, foot or face. About 40 percent of women aged 50 to 60 may have spider veins or varicose veins. Spider veins tend to look red or blue, with a thin, spider web appearance, while varicose veins may bulge like a rope under the skin. Both conditions tend to advance with age, especially among women.
Weak Veins
The immediate cause of spider veins, whether in the feet or legs, is a weakening of the veins that allows blood to trickle back into the vein. A variety of causes contribute to the weakening of vein walls, but the clogged, swollen vein in the foot is the most noticeable visible indication of spider veins. One-way valve flaps in the veins are meant to keep blood flowing back to the heart. When the flow becomes congested with blood collected in the veins, the vessels become visible. If they continue to swell, spider veins may progress toward becoming varicose veins.
Prolonged Standing
Prolonged standing places extra stress on veins in the foot and can cause the weakening of vein walls and blood congestion. Other factors, such pregnancy, also can cause the weakening of vein walls. Careers that force the person to stand for long periods, such as nursing, teaching, hair styling and factory work can be problematic for people with the tendency toward spider veins.
Heredity
Family history of blood clots as well as other vein and heart conditions can contribute to causing spider veins, according to the Cleveland Clinic. About half of those with spider or varicose veins have a family member with the problem.
Age
The likelihood that spider veins will form increases with age. About half of those more than 50 have difficulties with spider and varicose veins. Along with the weakening of veins due to aging, hormonal changes that come with age can also contribute to the problem. As a woman ages and has repeated pregnancies or if she gains weight with age, the probability of this issue increases.
