Spider veins are abnormally dilated veins that can be seen on the skin surface. Spider veins (also known as telangiectasia, thread veins, or broken veins) are the smallest or mildest form of abnormal veins and are classically blue, purple, or red in color.
By definition, they are up to 1 millimeter in diameter. Their fine branching pattern can look like lines, tree branches, or spider webs (hence their name).
They are almost always found on the legs or the face and can cover either a very small or very large area of skin. They can be asymptomatic and simply a cosmetic issue, but sometimes present with venous insufficiency symptoms such as pain, heaviness, swelling, and restlessness in the legs. Flow abnormalities in veins 1-3 mm in diameter, called reticular veins, can lead to the development of spider veins and are a critical consideration in spider vein treatment.
Conversely, varicose veins are simply the larger version of these abnormally dilated veins, measuring >3mm. They often look like cords and appear twisted and bulging. They can be swollen and raised above the surface of the skin.
Varicose veins are often found on the thighs, backs of the calves, or the inside of the leg. Varicose veins are generally a sign of more serious underlying venous disease and associated with symptoms.