It's easy to recognize unsightly leg veins as varicose veins and spider veins, but could you explain the difference between the two? A common question we get at The Vein Institute is what qualifies as a spider vein, and what qualifies as a varicose vein. Spider veins are less than 3 millimeters in diameter, making them too small to see on ultrasound. They are typically a blue or purple color. Less commonly, they have a reddish appearance. They are flat on the skin surface and can range from a few scattered veins to patches covering large areas. Although many people only have cosmetic issues with spider veins, some patients have reported itching or burning over the area of their spider veins. Varicose veins are greater than 3 millimeters in diameter. They are raised up from the surface of the skin and resemble a rope or snake beneath the surface. Varicose veins are typically far enough under the surface as to not affect the color of the skin. This also allows them to be easily evaluated with ultrasound. Recognizing vein disease can be tricky when appearances differ so greatly from person to person. Perhaps the most widely unknown fact about vein disease is that you can have it without any visible veins on the skin at all! Veins hiding under the surface can be the culprit for a wide range of symptoms. The key is to see a dedicated vein specialist, who can find answers for the way your legs feel and look.