Arteries bring oxygen-rich blood from heart to the rest of the body and veins return oxygen-poor blood back to heart. Varicose veins are swollen veins that we can see through skin. They often look blue, bulging, and twisted. Left untreated, varicose veins may worsen over time. Varicose veins can cause aching and feelings of fatigue as well as skin changes like rashes, redness, and sores. As many as 40 million Americans, most of them women, have varicose veins.