"The KTP laser is one of the group of lasers that acts by selective thermolysis of blood vessels and vascular lesions. The laser generates an intense beam of light. This beam brings energy to a specific site through a small handpiece connected to the laser. A cool tip is attached to the handpiece to keep the surface temperature down and so prevent thermal injury to the epidermis. The laser light is absorbed by the red blood cells, causing decomposition and destruction, whilst leaving the epidermal cells intact.
The leg vessels are substantially larger and have thicker walls that the facial vessels, or vascular malformation. Therefore, thermal heat diffusion from absorbed red blood cells requires a longer time to cause effective damage. In addition, leg veins are located deeper in the dermis that facial telangiectasia and protection of the epidermis with the cold tip is essential."