Normally, one-way valves in your leg veins keep blood moving up toward the heart. When the valves do not work properly, blood backs up into the vein. The vein swells from the blood that collects there, which causes varicose veins. Smaller varicose veins you that can see on the surface of skin are called spider veins.
Varicose veins are common, and affect more women than men. They usually don't cause problems for most people. However, in some people, they can lead to serious conditions, such as leg swelling and pain, blood clots, and skin changes.
Risk factors include:
- Older age
- Being female (Hormonal changes from puberty, pregnancy and menopause can lead to varicose veins. Taking birth control pills or hormone replacement can also increase your risk.)
- Being born with defective valves
- History of blood clots in your legs
- Standing or sitting for long periods
- Family history of varicose veins