Scientific studies in the early 1990s proved that lasers were an effective method of removing unwanted hair, and the first machine approved for laser hair removal in America was in 1996. Since then, many different types of Laser and Intense Pulsed Light (IPL) machines or Light Heat Energy (LHE) devices have been developed and improved to remove hair in all areas of the body. No manufacturer has been given permission to claim that they can cause "permanent hair removal", as this has not yet been proven. However, they are allowed to claim "permanent hair reduction", as that means that whilst hair may not be removed entirely and forever, it will certainly be removed to a significant degree. During the treatment a small hand piece will be used to touch your skin with flashes of light; a cooling spray, air or gel may also be applied. Most people describe the procedure as a little uncomfortable, with a tingling or stinging sensation. Treatments can be repeated at monthly intervals for between 2 and 7 treatments. Private costs for laser or IPL hair removal depend on the size of area treated and number of sessions required.