Thread veins are caused by a variety of factors including exposure to ultra violet light, wind and extremes of temperature. Steroid creams and the hormonal changes that occur during pregnancy can also induce thread veins.
Some individuals are genetically more prone to develop thread veins than others and some people are more at risk because of old injuries. If your parents had thread veins, then there is a good chance that you will develop them.
It is possible that hormone treatments, such as the contraceptive pill and HRT can increase the likelihood of forming thread veins.
