Varicose veins and spider veins are generally caused by: Genetics (if there is family history of varicose veins and spider veins, you may have them too). Jobs that require people to stand for long periods of time such as teaching, hair styling, nursing, factory work, etc. Long-term obesity. A medical history of blood clots. Drastic hormonal changes during puberty, pregnancy, and menopause. Hormonal birth control methods. Hormone replacement therapy during menopause. Anything that increases abdominal pressure such as girdles, constipation, tumors, etc. Major damage/injuries to the skin’s surface. Previous vein surgery. Aging.