Are varicose veins and spider veins dangerous?

Most people with varicose and spider veins do not go on to more serious problems, but there is an increased risk of some complications:

Phlebitis – clot and inflammation in a surface vein
Damage to the skin of the lower legs – Discoloration, thickening, or rash caused by inflammation in the tissues due to chronically elevated pressure in the veins.
Ulcers/sores – This is the end stage of skin and tissue damage from chronically elevated pressure in the veins. Often these ulcers will not heal without correcting the underlying vein problem.
Bleeding – Results from stretching and thinning of the skin overlying the vein and the vein wall from high pressures in the vein. Little to no trauma can cause the vein to break open and hemorrhage.
Deep Vein Thrombosis – Blood clot in a deep vein. It may cause symptoms such as pain in the calf or thigh or leg swelling. It may not cause any symptoms at all. If a portion of it breaks off it can travel to the lungs and may be fatal.