Sclerotherapy Q.   What are spider veins? A.   Spider veins are small, enlarged superficial blood vessels that appear red or blue. The cause of spider veins is not completely known. Q.   What is sclerotherapy? A.   Sclerotherapy is an injection method used to treat unwanted blood vessels. Using a very fine needle, sclerosing solution is injected directly into the blood vessel. Q.   How successful is sclerotherapy? A.   After several treatments, most patients can expect a 50 % to 90% improvement. Fading is gradual, usually over months. Q.   Can sclerotherapy be used on all skin types? A.   All skin types and skin colors respond equally well.