Lasers are devices that produce a highly-focused beam of light. They have numerous medical uses, including the treatment of dilated blood vessels and other vascular lesions. Various types of lasers, each generating a slightly different wavelength of light, can be used to target the dark pigment in the blood while passing harmlessly through the skin. The laser energy causes the blood vessel to coagulate (coh-AG-you-late) and the vein is gradually absorbed by the body. However, laser treatment tends to work best on veins that are three millimeters or less in diameter, or no bigger than a spaghetti strand. Spider veins on the face and some small veins on the legs, especially those which are closely matted, may be candidates for laser therapy. Usually, two or more treatments are needed to achieve the desired result. Larger and deeper veins on the legs are typically unsuited for laser treatment and may instead require sclerotherapy (sklair-oh-THAIR-uh-pee) injections or surgical removal procedures like phlebectomy (fluh-BEHK-toh-mee). Patients with dark or tanned skin may not respond well to laser therapy, due to a lack of contrast between skin pigment and blood vessels.