what causes spider veins

Spider veins are caused by abnormalities in the small blood vessels in the skin, primarily due to malfunctioning one-way valves in the veins. These valves normally prevent blood from flowing backward, but when they weaken or fail, blood pools in the veins, causing them to enlarge and become visible through the skin. Factors contributing to spider veins include age-related weakening of vein walls, heredity, hormonal fluctuations (such as during pregnancy or menopause), prolonged sitting or standing, obesity, sun exposure, injuries, and other conditions that increase pressure in the abdomen or legs. Spider veins may arise from venous or arterial origins and are often related to local oxygen deprivation causing inflammation and new vessel formation. They typically appear on the legs and face and may be linked to chronic venous insufficiency or varicose veins to a lesser extent.