Sclerotherapy is an injectable treatment for reducing leg veins.  An injection into the unwanted veins with a sclerosing solution causes the target vein to immediately shrink, and then dissolve over a period of weeks as the body naturally absorbs the treated vein.
Sclerotherapy is the "“gold standard"” for vein treatment and is preferred over laser for eliminating large or even small spider veins.  Unlike a laser, the sclerosing solution additionally closes the "“feeder veins"” under the skin that cause the spider veins to form, thereby making a recurrence of the spider veins in the treated area less likely.