Sclerotherapy is a microinjection procedure that requires no pain medication or surgery. Abnormal veins (spider veins) are treated by injecting a solution called a sclerosant. This seals the vein off from the rest of the vein network in your leg, allowing the body to naturally redirect the blood flow to healthy veins. A typical treatment may last from 15 to 45 minutes and will consist of multiple microinjections. May require 3-4 sessions.