Superficial leg veins, sometimes called "spider veins" occur when tiny veins congregate below the surface of the skin, causing red, blue or purple discolorations. Spider veins get their name from the shape of the discolorations. Some cases of spider veins can be quite small. Others are more noticeable. They may make you feel self-conscious, but they are harmless, and any treatment is usually done for cosmetic reasons only.
Spider veins are most common on the thighs, ankles and calves, and are more common in women than men. Their cause isn't completely understood in every case, but they can run in families. Some cases are related to pregnancy, use of birth control pills or weight gain.
Other types of problematic veins that can appear similar to spider veins include:
Telangiectasias, which are dilated capillaries close to the skin, and tend to be more noticeable on the face, whereas spider veins more commonly occur on the legs and feet
Hemangiomas and angiomas, which are made up of very small arteries called arterioles or very small veins called venules.
Sometimes, the terms spider veins and telangiectasias are used interchangeably.