Sclerotherapy can be used to treat both varicose and spider veins. A tiny needle is used to inject the veins with a medication that irritates the lining of the vein. In response, the veins collapse and are reabsorbed. The surface veins are no longer visible. Sclerotherapy relieves symptoms due to varicose and spider veins in most patients. With this procedure, veins can be dealt with at an early stage, helping to prevent further complications.