What causes spider veins?

Spider veins may be the result of an inborn connective tissue weakness and/or vein weakness with congestion (pooling) of blood in the vein system. With time, the delicate veins lose their original elasticity, becoming worn out and dilated.
The dilated veins can then be seen as bluish or reddish-purple spider veins shimmering clearly through the skin, particularly on the lower legs and the sides of the thighs.

Advancing age, natural hormonal changes (pregnancy and the menopause), hormone-based medicines such as the Pill, lack of exercise, standing for long periods at work, overweight, and smoking may all encourage spider veins to develop or make the problem worse.

Although in many cases spider veins are not considered to be a disease in the strict medical sense, they are a substantial cosmetic problem for many people.