During sclerotherapy, spider and varicose veins are injected with a medication that makes the lining of the vein walls swell and stick together, causing the damaged vein to seal shut. The flow of blood is stopped and, eventually, the vein disappears.

Sclerotherapy does not require anesthesia and can be done in the doctor’s office. It can be very effective, but several treatments may be necessary, and the veins may recur over time. Possible side effects include: discoloration, small skin ulcers and bruises.