Sclerotherapy is a medical procedure used for the elimination of small varicose and spider veins. It involves an injection of a medical solution directly into the vein via a tiny needle. The solution irritates the lining of the blood vessel, causing it to swell and stick together, which causes the vein to scar and collapse, forcing blood to reroute through healthier veins. Treated veins typically fade within a few weeks. In some cases, it may be necessary to have several treatments performed to achieve the desired results