There are many reasons why people develop spider veins. First and foremost, there is a strong familial (genetic) tendency that predisposes you to having this common condition – mostly on the maternal (mother’s) side.
Medications also may make you more prone to spider veins as well as social habits such as smoking which can affect your circulation. Prolonged sitting and standing may increase your chance of developing spider veins or make your spider veins worse.
There is research that also suggests that hormonal changes may have a role in whether or not a person will develop spider veins. Besides treatment (sclerotherapy or laser treatments), preventative measures to avoid smoking or excessive periods of standing or sitting can help in preventing or controlling spider veins.