Thread veins are a very slender vein especially one on the face that is visible through the skin how does it work the light is attracted to the target chromophore oxy hemoglobin in the blood as the blood in the vessels absorbs the light a heat reaction id caused which coagulates the blood and destroys protein in the wall of the vessel the vessel then breaks down and the debris is removed by the bodys natural waste disposal system scheduled 6 treatments to take place 1 every 4 week