Spider veins are very small veins caused by a dilation of the small veins under your skin. This occurs when the pressure inside the vein increases enough to overcome normal resistance of the vein wall. The ability of veins to resist increased pressure is reduced in women when the blood level of estrogen and progesterone is reduced.
Reticular veins are small, bluish colored veins that carry blood to the skin venules and therefore, are larger. These veins have thin walls and dilate with excessive venous pressure. When this occurs, they become large enough to be unsightly, but are not considered to be varicose veins.

Varicose veins are large, bulging veins often associated with tired, painful or achy legs. Sometimes varicose veins are deeper under the skin surface and not visible, however, the symptoms tend to be the same. Faulty valves in the veins, which allow some blood circulation to flow back instead of continuing on course to the heart, cause varicose veins.