What does one prevent spider veins or thread veins?

Good general health: Since these are from hormones and heredity it is not known how to prevent these except to stay in good general health.

There is something: The biggest factor in the development of spider veins is heredity which you can't help. Hormones and pregnancy also play a role. Obesity and trauma also play a role with spider veins which you can certainly help prevent by maintaining your weight and avoiding activities which lead to trauma.

Unfortunately you...: Really can't prevent spider veins, as drs. Wright and spitz said. Heredity is the biggest factor in causing them and you can't change who you chose for your grandparents. :) hormonal changes (puberty, pregnancy, birth control pills, estrogen replacement, etc.) play a role and, to some some degree, so does the aging process. If they occur and you don't like them, they can be treated.

Spider Veins: There are many factors that play a role in spider vein formation including genetics, hormones, aging, injuries, sun exposure and even weight. Keeping fit and exercising as well as wearing support hose may help. Often times spider and thread veins will occur despite doing preventative measures.