Why do spider-veins appear?

Spider veins are like varicose veins, only much smaller. Their appearance usually follows the same cause though.

It is believed that the primary physiological driver for this condition is a failure in the function of vein valves. The way veins work in our body is by pushing the blood only in one direction. When large muscles in our legs contract, they squeeze veins and push the blood upwards, against the gravity force. When muscles relax, tiny valves inside our veins prevent it from flowing backwards.  With age these valves tend to become weak and don’t maintain the stream of blood as effectively as before. When this happens the blood starts accumulating in small pockets, causing veins to swell and creating mini-bursts in the dermis layer.

However, the primary reason for appearance of spider veins is largely unknown. Some people appear to be more pre-disposed to this condition than others; whereas it can also be caused by hormonal changes, excessive sun exposure and skin injuries.