Spider veins are dilated small blood vessels that have a red or bluish color. While extremely common, spider veins are unnecessary and will remain until they are treated. A procedure called sclerotherapy is used to treat unwanted blood vessels and large varicose veins. A saline solution is injected with a fine needle directly into the blood vessel, causing it to swell, stick together, and the blood to clot. Over a period of weeks, the vessel fades, eventually becoming invisible. After several treatments, most patients can expect up to a 90% improvement.