Sclerotherapy is a treatment of varicose and spider veins. During sclerotherapy, a medication is injected into the vein using a tiny needle. This medication irritates the inner lining of the vein causing it to close. The closed vein is eventually reabsorbed by the body and will no longer be visible. Sclerotherapy relieves symptoms caused by varicose and spider veins. Many patients who undergo treatment for cosmetic reasons will also notice some improvement in the way that their legs feel after this treatment. Most people will need several sclerotherapy sessions to treat their veins. The actual number depends on the type, size and number of veins that are being treated. There is little or no pain during the treatment. You will feel a small pinch when a needle is inserted and may have a slight, itchy sensation afterwards at the site of injection.