When we are in a hot shower and standing there is a lot of vein pressure bringing the circulation toward your feet. If you suffer from varicose veins it is difficult for that blood to return back to the heart. A hot shower will also cause the vessels to dilate and there is an increase in pressure bringing the flow upward. The skin softens over the weakened vessel and with the increase in circulatory pressure the potential to break the vessel open and bleed is increased.