Sclerotherapy is the most common treatment for spider veins. It can usually be performed on an outpatient basis with very little scarring or side effects. During sclerotherapy, a solution containing saline and other chemicals is injected into the vein with a very small needle. The solution causes the vein to close or collapse, greatly reducing or even eliminating its appearance. Sclerotherapy may require multiple treatments of one to three injections per vein (more than one vein can be treated at a time in one session).