Varicose and spider veins are damaged veins. We develop them when tiny, one-way valves inside the veins weaken. In healthy veins, these valves push blood in one direction — back to our heart. When these valves weaken, some blood flows backward and accumulates in the vein. Extra blood in the vein puts pressure on the walls of the vein.

With continual pressure, the vein walls weaken and bulge. In time, we see a varicose or spider vein.

Some people have a higher risk of developing these veins. If blood relatives have them, you have a higher risk. Many people get them because they sit or stand for long periods most days of the week. These veins also become more common with age and during pregnancy.

Spider veins can also be caused by sunlight, hormonal changes, or an injury.